This is borderline ASB, but I'll give it the old college try. Michigan Governor (and Willard's father) George Romney was a frontrunnner for the Republican presidential nomination in 1968. In our timeline, he largely blew his chance at the nomination following a series of gaffes. The most prominent was his now-infamous claim that the American military "brain washed" him into thinking that the United States was winning the Vietnam War. The point of divergence is that Governor Romney does not make that fateful error and instead runs a solid campaign. He does well in the Republican primaries and heads to the convention with momentum and the support of party moderates. After denying Nixon the nomination on the first ballot, Romney wins the second ballot. He goes on to win a narrow victory against Hubert Humphrey in November. President Romney paves a moderate record, much like Nixon's. He pulls out of Vietnam earlier, begins a period of detente with the Soviet Union and China, and makes several failed attempts at reforming government programs (think FAP and health care reform). Romney wins reelection in 1972 by a comfortable margin, defeating Hubert Humphrey once again. Romney's Vice-President, John Tower, narrowly defeats Senator Birch Bayh in 1976. However, his term is plagued by economic problems and an increasingly strenuous world. He is defeated by Ted Kennedy in 1980. Kennedy presides over eight years of improved economic and world conditions. He passes health care reform, expands federal anti-poverty programs, and raises taxes on high-earners. He is a controversial President, but wins reelection in 1984 over Senator George Bush. The second half of his Presidency is less successful, and the Republicans are the favorites to take back the White House in 1988.
Meanwhile, Mitt Romney goes to college and business school before joining the Bain & Company financial firm in 1977. He turns the company around and is viewed as a rising star within the financial world. In 1982, Romney decides to follow in the footsteps of his father and run for Governor of Michigan. Touting his business record and his father's successful Presidency, Romney is able to defeat Democratic Congressman Jim Blanchard. Governor Romney balances the state budget, cuts taxes for businesses, and works to improve education and anti-poverty programs. He's reelected in a landslide in 1986. Touted as a promising candidate for the Presidency in 1988, Romney jumps into the race in the Summer of 1987. He raises great deals of money from his financial connections and friends of his father, and is soon outpacing frontrunners Senator Bob Dole and Governor Jack Kemp. Running ads that tout his record as a "common sense, no-nonsense, Governor" and claiming that "he'll do for America what he did for Michigan," Romney gains ground in the polls. Largely ignoring Iowa, Romney puts most of his resources in New Hampshire. His strategy pays off as he easily defeats Dole and Kemp in the state. Romney stays positive for most of the campaign, and manages to do very well on Super Tuesday. He is able to wrap up the nomination by the end of the spring. Romney chooses Indiana Senator Richard Lugar as his running-mate, and the two go on to narrowly defeat Vice-President Dale Bumpers in the general election.