C.J.'s first day as Chief of Staff gives her a new appreciation for Leo's skill in the role. While struggling to keep up with her hectic schedule, she must handle the sudden appearance of abandoned Soviet nuclear material, counter political maneuvering within the Cabinet, and assert her authority with the staff and the President. Toby conducts a press briefing after which C.J. orders him to quickly find someone to fill the role permanently. The Democratic Party enlists Josh's help to talk Congressman Matt Santos out of taking an early retirement.

Josh visits a car dealership and is seduced by both a hybrid and a monster SUV, despite knowing that Congress is unlikely to raise fuel efficiency standards. For political cover as well as genuine concern, he meets with representatives of the alternative energy industries. Charlie has graduated from college and is reluctant to keep his promise to the President of finding a "real" job. Following press complaints about Toby he agrees to take deportment lessons from Annabeth. C.J. visits Leo at his hotel and finds out why he's so insistent that the President play chess each week.

The glow of the Middle East peace deal begins to fade once the hard reality of implementing change begins. Josh becomes involved in the Patient's Bill of Rights, which is becoming a political football as the Vice President and Congressman Santos both try to out-maneuver each other and the Republicans. C.J. continues to be unimpressed with Toby's performance as press secretary when he gets into a difficult position during a briefing. While working to recover from his heart attack, Leo receives a job offer from the corporate world.

Magicians Penn and Teller give a controversial performance at Zoey's birthday party in the White House that threatens to drown out the news of the impending China trip. President Bartlet goes to New Orleans on his way to China after unexpectedly requesting briefings be postponed until they are in the air. Josh tries to decide which Democratic presidential candidate he wants to support, and is alarmed that Bartlet wants to appoint California Republican Senator Arnold Vinick to be Ambassador to the United Nations.

President Bartet's attack of multiple sclerosis requires hasty reorganization of the summit in China. Unable to endure the long meetings, he becomes frustrated when the Chinese take advantage of his absence to drag their feet over North Korea. Back at the White House, Josh is told by NASA that a large asteroid is on a collision course with earth; staffers are unsure whether to prepare for the end of the world or not. Donna becomes frustrated when Josh continually postpones what she says is an important conversation. With the New Hampshire primary looming and Vinick looking like a formidable opponent, Josh and Leo try to find a Democratic presidential candidate they can believe in.

On the same day that an anti-gay-marriage amendment is attached to the federal budget, an Internet rumor surfaces that C.J. is a lesbian. Josh and Toby attempt to kill the amendment without forcing the President to publicly take a position on this unwinnable issue. Congressman Santos considers Josh's proposition that he run for President despite having told his wife that he's done with politics. Donna begins her new job while Josh struggles to cope with her difficult replacement. Abby and C.J. meet with the President's doctors to decide how to adapt his schedule to the increasingly debilitating effect of multiple sclerosis.

Leo returns to the White House to help bolster the administration, which is suffering from the loss of Josh, Donna, Will, and the Vice President to the next election campaign. Leo's first day back follows President Bartlet's last State of the Union address, and unlike in previous years there appears to be little momentum on bold, large-scale initiatives. Amidst numerous distractions that dilute the focus of the staff (kidnappings in Colombia, the First Lady's appearance at a NASCAR race, and petulant Congressmen), he challenges the administration on their agenda for their remaining year in office.

CJ and Abbey go twelve rounds on how to handle President Bartlett and his disease. Lord Marbury makes his return to the White House after a British commercial plane gets shot down by Iran. Toby splits his time between helping write a Belarus constitution and the yearly meeting with Miss World

Back in Washington briefly, Josh visits the White House and is surprised to discover that as a campaign manager he is no longer part of the inner circle in an administration that wants to remain neutral in the Democratic primary. Toby is the focus of some concern after being more withdrawn than usual and also because he is nursing a cut on his face that he doesn't want to talk about. Charlie tells Kate that a guy at his gym has been asking about her, but she's unsure if she's ready to date again. A multi-state water rights fight pitches C.J. against lobbyist Cliff Calley, who proves to be both infuriating and intriguing. Josh and Donna are both suspicious when far-left Senator Rafferty joins the race, obviously as a spoiler candidate.

The Speaker of the House deliberately calls a vote on stem cell research when he knows that Democrats will be away from Washington; Donna, Cliff, Matt, and Josh must put aside their differences to foil the plan. Kate is shocked when a minor hunting mishap on the Canadian border threatens to become a major international incident. A Japanese economist who has been President Bartlet's arch-rival since college is attending a formal dinner at the White House, creating a potentially explosive situation. Toby tries to avoid meeting with a group of middle school children who want a constitutional amendment lowering the voting age.

Senator Arnold Vinick easily wins the Republican nomination on the night of the New Jersey primary, but has difficulty picking a running mate. Choosing Reverend Don Butler would virtually guarantee him the presidency, but their differing views on abortion and religion would make it a political union rather than one based on shared ideology. The Democratic nomination is a toss-up between Santos and Russell; Hoynes is running a distant third. With no clear nominee going into the convention, the Democratic party risks appearing unsure about both Santos and Russell - a position that President Bartlet does not want the Republicans to be able to exploit.

While Vinick and the Republicans deliver a flawless albeit predictable convention, the Democratic convention looks to be more like a pie fight as there is no clear favorite. Russell tries to preempt the floor vote by hinting offers of the vice presidential nomination to both Santos and Governor Baker of Pennsylvania. Charlie and Zoey's relationship is becoming more serious, resulting in different reactions from the President and the First Lady. An air leak on the International Space Station will kill all three astronauts unless a rescue mission can be launched. NASA advises that their shuttles are unfit for flight, but then hints at another solution.

WHO WILL BE THE DEMOCRATIC PRESIDENTIAL CANDIDATE? - It's the Democratic National Convention and the race to become the Democratic Presidential candidate has narrowed to three candidates: Russell, Baker and Santos. Also, Bartlet must wrestle with the decision to launch the super-secret defense shuttle to rescue the astronauts trapped at the space station and risk national security or let them die.

Four days after the Democratic convention, Josh begins to staff up the Santos campaign. With Santos and Leo effectively strangers - and Leo not an experienced campaigner - adjustments of roles and responsibilities are required in order to deliver a strong and consistent message. The White House prepares to launch the military Space Shuttle on its rescue mission to the Space Station amidst growing suspicion that proof of its existence was deliberately leaked by someone in the Administration. The Republicans offer Bartlet a concession on an education bill in an attempt to drive a wedge between him and the Santos campaign.

Despite vigorous campaigning, the Santos campaign still struggles to articulate its message and keep the focus on domestic issues rather than gossip and trivia. Although Santos served decades in the military and remains in the reserves, Vinick still appears the stronger candidate on national security issues due to stereotypes about Republicans and Democrats. The White House's decision to halt their own investigation into the leak is a savvy legal move, however it could prove to be costly politically: while Vinick can slam the President for this decision, it's not so easy for Santos to do so. Josh reluctantly recruits help with running the campaign when it becomes obvious that he's trying to do too much himself.

With Santos gaining momentum, the Vinick campaign devises a strategy to catch them off-guard by focusing on immigration issues: by taking a pro-immigration stance, they force Santos to spend time courting the Latino vote. A powerful Christian group is nervous about supporting a Republican presidential candidate who is pro-choice, and demands a guarantee that Vinick only appoint pro-life judges. Vinick hopes that the strong religious credentials of his running mate Sullivan will be enough to satisfy the Christian base, but inevitably finds himself in a difficult situation.

The Santos campaign faces questions on intelligent design and evolution during a campaign stop focusing on education in Pennsylvania. Margaret testifies before the committee investigating the leak, which has also served most current and former members of the Bartlet administration with subpoenas. A suicide bombing in the Middle East throws the region into chaos and threatens to postpone all campaigning. An intelligence analyst assigned to brief the Vinick campaign demands to speak with CJ.

A pro-life special interest group launches an ad attacking Santos for his abortion stance, but Vinick also sees it as trouble since he's also pro-choice and doesn't want to draw attention to the issue. With Vinick ahead in the polls, he has no incentive to debate Santos and thus continues to drag his feet over negotiations. Back at the White House, C.J. orders new Communications Director Will Bailey to not answer questions from the press about the leak investigation.

A live debate between Santos and Vinick, performed once for the east coast and once for the west.

The Santos campaign's difficulties with the black community continue when a Latino police officer shoots a black child; C.J. offloads preparations for Ellie's wedding to Will when Kate needs her help with Kazakhstan; Josh visits Toby.

President Bartlet's plan to attend his daughter Ellie's White House wedding is jeopardized when Russia and China mobilize troops over growing chaos in Kazakhstan. The Santos campaign has gained ground on Vinick over the last few weeks, but with less than two months until the election it's not clear that the gap can be closed. As Josh obsesses over the electoral math, tracking polls, and decisions on where to spend advertising money, some Democrats are nervous that the election is slipping away, and urge Santos to fire Josh as campaign manager.

Leo's preparation for the Vice Presidential debate is going badly; Santos makes his last trip home before the election; Will and Kate continue to flirt.

Danny tells C.J. some important news about the President's son-in-law over dinner; C.J. attempts to broker an international deal to stop genocide in Darfur; Josh twists C.J.'s arm to get her to help the Santos campaign.

A nuclear accident in California sends the White House and both campaigns into overdrive. Meanwhile, China and Russia appear headed for a showdown over elections and oil in Kazakhstan.

The Vinick campaign struggles with the impact of the nuclear accident in California; Josh and Donna have a "moment".

Both candidates face vital choices about which states to campaign in; Vinick tries to put the nuclear issue behind him; Bruno finds Santos's briefcase.

A federal prosecutor's threat to indict Toby on another charge has the potential to affect the impending election.

Election day finally arrives; C.J. ponders job offers; the election looks too close to call.

Polls are closing across the country, and the race is too close to call; friends and colleagues react to the news about Leo.

President Bartlet and his current and former staffers come together for Leo's funeral.

Eyebrows are raised when the President-elect places a call to the president of China and offers a different position than that of Bartlet. Meanwhile, Josh picks his deputy chief of staff.

While Santos is wrapped up in choosing his new Vice President, Helen is overwhelmed by the issues facing the new First Family. Meanwhile, Vinick must find a new road now that the election is over.

Two weeks before the inauguration, CJ and the rest of the Bartlett administration consider what they will do next. CJ examines her relationship with Danny and considers whether or not to suggest to the President pardoning Toby.

Santos and his staff prepare for the inauguration as Bartlet and his team look back on their years in the White House.

Leo returns to the White House to help bolster the administration, which is suffering from the loss of Josh, Donna, Will, and the Vice President to the next election campaign. Leo's first day back follows President Bartlet's last State of the Union address, and unlike in previous years there appears to be little momentum on bold, large-scale initiatives. Amidst numerous distractions that dilute the focus of the staff (kidnappings in Colombia, the First Lady's appearance at a NASCAR race, and petulant Congressmen), he challenges the administration on their agenda for their remaining year in office.

Josh visits a car dealership and is seduced by both a hybrid and a monster SUV, despite knowing that Congress is unlikely to raise fuel efficiency standards. For political cover as well as genuine concern, he meets with representatives of the alternative energy industries. Charlie has graduated from college and is reluctant to keep his promise to the President of finding a "real" job. Following press complaints about Toby he agrees to take deportment lessons from Annabeth. C.J. visits Leo at his hotel and finds out why he's so insistent that the President play chess each week.

Leo's preparation for the Vice Presidential debate is going badly; Santos makes his last trip home before the election; Will and Kate continue to flirt.