Could he become President earlier or later? The earliest election he's eligible for is 1984. What if Nixon chooses Bush as his VP in '73 then resigns? George W. Bush gets his act together and gets into politics earlier becasue of this (his dad doesn't want more embarrassments after having just become VP - and then President - during the scandal-ridden Watergate years.
Reagan beats Bush in '76 for the primary election but loses to Carter - Carter then wins narrow re-election in 1980 over someone like Bob Dole who is kind of blah as a campaigner, while the economic malaise during the Carter years propels the younger Bush into Congress.
The Soviet Union is still teetering ont he brink of collapse when the '84 election cmes around, and Bush Sr. is still old enough he considers giving it another run - he didn't in 1980 for some reason. (some scandal on his part?) Also, there's still some desire for a conservative.
Enter the younger Bush - a confused primary season sees him squeak by with a victory, and the economy is just picking up int he last year after another downturn in '82, and the GOP has both houses.
So, we get Bush as President while the Cold War is winding down. His V.P., Howard Baker, is a moderate who is known for working with Congress and also known for doing well in foreign affairs, and is old enough to give the younger Bush the clout needed to beat MOndale, who is seen as too liberal. Baker also is the man behind the scenes working to get Bush the meetings with Gorbachev to start mending fences and "winning the Colde War" while Bush uses people like Samantha Smith, who wrote a letter to the previous Soviet leader, as an example of how the people can be empowered to lead, calling her "one of a thousand points of light to light the darkness of this crazy world." (He also borrows some phrases from his dad, whom he appoints as an ambassador.)
The economy starts booming under him, and as the Berlin Wall crumbles in his 2nd term, he gets credit for "winning the Cold War," and also bringing confidence back to America. His 2nd term is where he'll really establish a legacy as not just a pretty good President but a great one, but I don't know how to do that one. Anyone want to take it from here? He at least has a fighting chance if things break right. If the planned attack on the world Trade Center is plotted a year or two early and he manages to stop it, that would help. Maybe he uncovers a bigger threat that comes about becasue of the terro threat? (I did a paper on terrorism in high school in the mid-'80s and it was a worry then, so it's possible there could be attempts on our shores that he prevents.)