To avoid a potentially explosive scandal when the U.S. President goes into a coma, an affable temp agency owner with an uncanny resemblance is put in his place.
Bill Mitchell is the philandering and distant President of the United States. Dave Kovic is a sweet-natured and caring Temp Agency operator, who by a staggering coincidence looks exactly like the President. As such, when Mitchell wants to escape an official luncheon, the Secret Service hires Dave to stand in for him. Unfortunately, Mitchell suffers a severe stroke whilst having sex with one of his aides, and Dave finds himself stuck in the role indefinitely. The corrupt and manipulative Chief of Staff, Bob Alexander, plans to use Dave to elevate himself to the White House - but unfortunately, he doesn't count on Dave enjoying himself in office, using his luck to make the country a better place, and falling in love with the beautiful First Lady...
Dave Kovic is the happy-go-lucky and much beloved owner/operator of Kovic's Temps, a temporary placement employment agency, he working his hardest to find jobs for his clients, the motto to which he strives being, "It's Monday. Everybody works on Mondays," or whatever day of the week it happens to be. Beyond this job, he, a showman, also does work impersonating a famous figure to who he has an uncanny resemblance: current US President Bill Mitchell. Through the President's primary secret security agent Duane Stevenson on behalf of White House Chief of Staff Bob Alexander and White House Communications Director Alan Reed, Dave is asked to pretend to be the President at a public function, they stating as the open venue places the President at an undue security risk. Dave's role would last for less than a minute as a walk-through, with he not to say anything during the public appearance. They also state that having a double for the President in such cases is regular procedure. What they don't tell Dave is the real reason for them needing a double is so that the President can carry on an extra-marital affair with one of his staffers at this time and thus have an iron-clad alibi if ever caught. Following this public event, they ask Dave to continue the work, as the President has suffered a serious health issue, in reality, they again not telling Dave the details, it being a major stroke that occurred during that sexual liaison, which has resulted in him falling into a coma from which he will never recover if he survives at all. What they also don't tell Dave is that instead of passing the Presidency onto Vice-President Gary Nance - who they coin a "boy scout", but who they tell Dave is mentally unstable - Bob has his own designs on the Oval Office, which will entail he and Alan coming up with some scandal to pin on Nance. Bob and Alan have to tread lightly as Bob, in conjunction with President Mitchell, has committed major crimes in the past which could land them in jail, this fraud with Dave being just the latest. Beyond learning the logistics of being President Bill Mitchell, Dave has to fool those that know the President, most importantly the First Lady, Ellen Mitchell. Things become more complicated when Dave senses an opportunity to do something good in his tenure as President, and as he starts to have feelings for First Lady Mitchell, who in turn hates her husband for his known marital infidelities. These items could place Dave in direct conflict with his employer, namely Bob.
Dave Kovic looks so much like President Bill Mitchell that he's asked to stand in for him, while the Bill occupies his time elsewhere !. When Bill falls into a coma, a secret and highly illegal plot is hatched by Bob Alexander to keep Dave on as the president. Unknown to Dave, Bob is working on making himself president, but he doesn't count on Dave being so popular and keen to continue.
President Bill Mitchell is not exactly an ideal President. He looks after those who helped get him into office than the people, and he is a philanderer. One of the ways that he keeps his little dalliances a secret is to hire a lookalike to impersonate him and when he is at a function at a hotel, his double is the one the press and media see leaving the hotel, while he stays behind for his little rendezvous. Now the man whom they have hired is Dave Kovic, a goodhearted man who likes to help people find jobs. Normally after making his little exit that would be that but Mitchell suffers a stroke. Now he is completely incapacitated, and by law the Vice President will assume his duties but Bob Alexander, Mitchell's Chief of Staff who is just as corrupt and ammoral as Mitchell maybe even more, fears that the Vice President who is boy scout, will probably not play ball with him or not keep him around, tells Dave that it's in the country's best interest that the Vice President not take over. So he agrees to continue pretending to be the President. But in reality Alexander is planning to smear the Vice President into resigning thus paving the way for him to be President. But when Dave becomes infatuated with the First Lady, and when Bob acting in Mitchell's place, cuts off funding to one of her projects, she assumes that it was Dave as Mitchell, who did it. And so to make it up to her, he restores the funding, which infuriates Alexander. Which means that Dave and Alexander are headed for a clash.
- Dave Kovic (Kevin Kline) runs a temporary employment agency in Georgetown, Washington, D.C.. As a sideline, he makes appearances impersonating President William Harrison "Bill" Mitchell, whom he has an uncanny resemblance to (and who is also played by Kline). One Mitchell's devious Chief of Staff, Bob Alexander (Frank Langella), hires Dave to make an exit at an appearance of President Mitchell, to cover up Mitchell's extramarital affair with White House staffer Randi (Laura Linney).
When the real President Mitchell suffers a stroke while having sex with Randi, he is left in a coma. Alexander sees an opportunity, and along with Communications Director Alan Reed (Kevin Dunn), he arranges for the President's comatose state to be kept secret. They then con Dave into impersonating the president on an ongoing basis by telling him that the country would suffer if the truth was revealed or if Vice President Gary Nance (Ben Kingsley), who they claim is mentally ill, took office. Apart from them, only his Secret Service bodyguard, Duane Stevenson (Ving Rhames) and the medical staff tending to the real President Mitchell in the White House basement (and who are being paid hush money by Reed), know the truth. Neither Mitchell's mistress Randi nor First Lady Ellen Mitchell (Sigourney Weaver) is informed of the switch.
Alexander's true agenda is to exercise the power of the presidency through Dave as a proxy in the short-term, while in the long term framing Nance for illegal activities, allowing Alexander to succeed Nance as Vice President, and ultimately become President himself. However, Dave gradually sets his own course of action, which revives Mitchell's popularity with the public and mystifies both the Washington media (several well-known personalities make cameo appearances as themselves) and the First Lady, whose public support of her husband has been a cover for bitter marital strife in their private life. Michell calls on his friend Murray, an accountant from Baltimore, to rework the national budget in order to find $650 million. He uses the money to save a favorite program of the First Lady, a homeless project. The First Lady tricks him into exposing his ruse. Caught, he convinces Stevenson to take her to see the real President Mitchell, who is not expected to live. The First Lady has a minor breakdown and decides to leave the White House. Dave realizes he has a chance to actually help the nation and convinces her to remain and keep up the ruse for a while longer. Despite Ellen's cynicism, she is soon charmed by Dave's sincerity.
When Alexander realizes that Dave is no longer his puppet, he threatens to expose him, but Dave stands up to him and points out that Alexander has more to lose from revealing the fraud. Dave then holds a news conference announcing that he is firing Alexander, and proposing a comprehensive full-employment program to Congress.
Dave meets Vice President Nance, who had been sent off on a goodwill tour of Africa. Nancu chastises "Mitchell" for framing him in a financial scandal. Dave realizes that the affable Nance isn't mentally ill as Alexander had insisted, but that Alexander has been using him. Alexander tries to destroy Dave by implicating him in the same financial scandal - only this time, as Communications Director Reed tells Dave, the real President Mitchell is actually guilty. At the same time, Alexander pushes his own candidacy for the presidency.
During the uproar over the scandal, Dave refuses to stop pushing his employment bill. He also bonds with Nance one night when Nance discusses his rise from being an unhappy shoe salesman to being the Vice President. Dave and Ellen agree that Nance is a genuinely public-minded man, and would make a fine president.
In a joint session of Congress, Dave, as Mitchell, admits to his role in the scandal, but introduces evidence (provided by Reed) proving that Alexander was the mastermind and that Nance was innocent. In the middle of making a formal apology to the nation, Dave fakes a stroke and is switched with the still-comatose Mitchell. Mitchell is then declared incapacitated under the 25th Amendment, and eventually dies. The groundswell of affection generated by Dave's brief time in office is transferred to the real Mitchell, as the public and the media mourn his death. The ruse apparently remains undiscovered; although Bob Alexander is later arrested and indicted, there is no indication that he reveals the secret, since doing so would compound his liability. Nance becomes President and promises to carry out "Mitchell's" employment program.
Five months later, Dave is running his own campaign for city council. Former First Lady Ellen Mitchell, now a widow, comes into the office "seeking a job," and they kiss. When he closes the shades in the window of his office door, Stevenson steps in front, wearing a campaign badge for Dave.