Mackenzie Allen, who serves as Vice President of the United States, has a tough decision to make, whether or not to go against the wishes of the dying current President. He has asked her to step down and let someone a little more appropriate take his place in the Oval Office. However, it's not only the President that is calling for her resignation, it's her entire party which elected her as the Vice President to start with.

Mackenzie Allen begins her transition into the office of the President. Her first order of duty is to select a Vice President and Nathan Templeton tries to use the situation to his advantage. Meanwhile, Rebecca's diary goes missing and she worries that the information about her mother in the diary will hurt Mac. Also, Mac's speech writer has a tough time learning the ropes.

Faced with her first national crisis - the passing of nine DEA agents in Latin America - Mackenzie shows strength and resolve in dealing with a corrupt leader. Meanwhile, Nathan Templeton is approached by an ambitious congressman who served with Mac's Vice Presidential candidate, Warren Keaton, and is eager to divulge potentially damaging info in an effort to derail his nomination. Mac's teenage twins resume public school, only this time it's complete with secret service detail and press spectacle, and while popular Horace welcomes the attention, shy Rebecca finds it overwhelming.

All eyes are on Mackenzie Allen as she hosts her first official summit with the Russian President - which is threatened to be overshadowed by Nathan Templeton's plan to engineer a series of cabinet resignations to coincide with the summit. Templeton goes after Mac with a vengeance, vowing to run - and win - against her in the next presidential election. Meanwhile, as First Gentleman, Rod must host his first state dinner for the Russian President and his wife.

In the middle of the announcement of her new National Security Advisor, Anthony Prado, Mac is caught off guard by the breaking news of a terrorist smuggling explosives across the Canadian border. The way in which Mac and her Attorney General deal with the situation pits them squarely against each other, and Nathan Templeton takes great pleasure in publicly second-guessing Mac's every move. Meanwhile, it's Halloween, and Amy - who desperately wants to go trick-or-treating like a normal kid - is disappointed to learn that, due to security concerns, she may have to settle for a party this year instead. When Rod as First Gentleman finds himself fodder for late-night comics, it hits his son Horace especially hard.

A hurricane strikes the Florida coast and Mac and Templeton fly to the scene to survey the damage. In Florida, Mac learns of an emergency situation involving an oil tanker that could have potentially devastating results. Meanwhile, Rod debates taking the Baseball Commissioner position and Rebecca convinces the Secret Service to give her space so she can spend time alone with the boy she likes.

A book is released about Mackenzie, and when confidential information is exposed, suspicions begin to arise. Warren Keaton begins his confirmation hearings, but his confirmation becomes at risk when events from his past are revealed. Meanwhile, Horace worries about his bad grades while Rebecca and her new boyfriend get closer.

Mackenzie decides to change the direction of her administration - from reaction to action - and appoints Rod as Strategic Planning Adviser, much to the disgust of Chief of Staff Jim Gardner. Meanwhile, Vince's drug test reveals that he's HIV positive and Templeton plots to use this to his advantage. Mac is presented with scandalous information about Templeton's past and has to decide how to use the information. Later, Horace almost gets into a fight with Rebecca's boyfriend when he learns about the rumor he's spreading.

As Thanksgiving rolls around, Kate Allen, Mac's mother, comes to the White House for the holiday. Mackenzie invites Templeton and his wife for dinner, which Kate insists on cooking. Meanwhile, Rod brings in Richard "Dickie" McDonald, a media consultant, to help with Mac's image and lagging poll numbers. Mackenzie also must decide the fate of a woman on passing row.

Mac must deal with her largest crisis yet when a U.S. submarine off the coast of North Korea runs into trouble. Meanwhile, Mac debates running in the next presidential race with Dickie McDonald as her campaign adviser. Each of her family members, except Rebecca agree with her decision.

While trying to coordinate the rescue of the crew of a damaged U.S. submarine off the coast of North Korea with help from Chinese, Mac must deal with war fever among her advisors and a leak from China to the North Korean government that threatens to start a nuclear war. Meanwhile, Speaker Templeton's wife secretly encourages Jayne Murray to accept Nathan's offer to rejoin his office as chief of Staff.

Templeton and Mac fly out to the dedication former President Bridges Presidential Library. When they land in California, Air Force One is held hostage by a man who wants to speak to the President or he'll blow up the plane. Meanwhile, Kate allows Horace and Rebecca to throw a party while Mac and Rod are out of town, not realising the potential consequences of doing so.

While Mac is busy preparing for her first State of the Union Address, Rod, after drinking at a reception, finds himself in a compromising position with an intern, with cameras around him all the while. When the photos are printed in the papers the next morning, the scandal threatens to overshadow Mac's State of the Union. Meanwhile, Templeton takes it upon himself to sabotage Mac's Homeless Initiative Bill.

Carl Brantley, Mac's nominee for Attorney General, takes a hit from the Senate during conformation hearings due to his actions towards crime, but Mac remains sure in her nominee. Meanwhile, a plane carrying weapons goes missing over Pakistan and Vice President Keaton takes charge of the situation using his military experience. Rod begins to settle into his role as First Gentleman, but when Kate goes missing, Rod, and the rest of the family, become panicked.

Mac wants her Attorney General to look into an urban situation in Maryland because it's where Gardner is from. Mac is also briefed on the situation of the missing surface-to-air missiles that went down in a military plane crash over Pakistan and has to make sure that the weapons do not end up in the hands of terrorists. Templeton is ralling support for the Templeton Act which focuses on domestic crime and Mac is threatening to use her veto power in the hopes for more law enforcement and education over the bill's calls for tougher sentencing. Dickie learns that Vince is planning a commitment ceremony with his partner and he warns him not to invite Mac because it might hurt her in the polls.

When Mac's appendix bursts on Air Force One, Templeton becomes acting President since the Vice President is not on board. Meanwhile, the airline strike is taking a toll on Memorial Day weekend air traffic, one of the busiest travel times of the year, and Templeton, viewing his unique opportunity as a test-drive for his Presidential plans, handles the situation in a unique manner.

On Mac's birthday, she is faced with the fact that there are American hostages being held in Turkey by a militant Kurdish group. Meanwhile, she also has to interview new candidates to be her Vice President and Dickie tries to convince her of the type of person she needs to choose because her choice will affect her re-election campaign.

When a longtime outspoken critic of the Equal Rights Amendment passes away and his wife prepares to take over his Congressional seat, Mac sees the opportunity to amend the Constitution and finally pass the ERA. Meanwhile, she prepares to participate in a previously scheduled Get Out the Vote event with Templeton, which turns into more of a presidential debate. On the home front, Rod is approached about doing a story on his relationship with Mac a Presidential marriage and it turns out Kelly has a past with the writer. Rebecca continues her relationship with her IM buddy, but theyre each shocked at the others identity when they meet in person. And the differences between Mac and Dickies beliefs become glaringly apparent.