Mackenzie Allen, the 45 year-old Vice President, has to chose whether or not to grant the final wish of the dying President: step down and let someone else take office when he passes. Mac's entire party agrees with the President, but Mac is determined to be President despite the obstacles and judgment she'll face.
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.
When Mackenzie is faced with her first crisis - the death of nine DEA agents - she is able to show her leadership and strength to the nation. Templeton meets with a congressman, Warren Keaton, who wants to damage Templeton's nomination. Meanwhile, Mac's twins return to public school, but must attend this time with secret service, which Horace loves, but Rebecca hates.
Mackenzie hosts her first official summit with the Russian President, but Templeton's plan to force cabinet resignations threaten to overshawdow the event. Templeton goes after Mac and vows that he will win against her in the next presidential election. Meanwhile, Rod has to host his first state dinner for the Russian President, since it is a duty of the First Gentlemen.
Mac must deal with a potentially deadly situation when she learns that terrorists have smuggled explosives across the Canadian border. Mac's course of action conflicts with the Attorney General's, and Templeton enjoys being able to publicly second guess Mac. Meanwhile, Amy is sad to learn that she'll have to have a Halloween party instead of trick-or-treating, due to security concerns, and Horace has a hard time dealing with Rod being poked fun at for being First Gentleman.
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 death 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.
The situation in North Korea begins to escalate and Mac's leadership tried as the country worries about a potential nuclear war. In the midst of the crisis, Templeton's leadership is shown to be contradictory to Mac's, and the nation sees how having Templeton running the country may lead them a different outcome than Mac's administration.
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 has her Attorney General investigate the cause of the growing urban unrest in Prince George’s County, Maryland. Mac learns that the county is where Chief of Staff Jim Gardner is originally from while Gardner has an unexpected visitor from the past who tells him about the situation in Maryland. Meanwhile, Mac must deal with a crisis when surface-to-air missiles that were lost in a military plane crash over Pakistan have resurfaced on the black market. Templeton continues to campaign for the Templeton Act, which Mac threatens to veto.
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.
It's Mac's birthday, but her celebrating is put on hold when Americans are taken hostage in Turkey by a militant Kurdish group. Meanwhile, Mac continues interviewing candidates for Vice President, and Dickie voices his opinion about who Mac ought to chose. Also, Rebecca's IM friend ends up to be someone unexpected.
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.