Would the swing states be the same with two different candidates? If someone else won the GOp nom?
They’d be pretty much the same, regardless of the candidate. Over the last 20 years or so, there are some states that one knows will vote Democratic (Illinois, New York – states with large urban populations), some that will vote Republican (Wyoming, Mississippi – states with large rural populations.) The “swing states” are (largely) states where the urban and rural populations are pretty much equal, so that a small number of votes can make a diff.
While an individual candidate might change a single state (say a home state) it’s unlikely that a fleet of them could change at once based on a candidate.
Swing states do, however, change over time. There was certainly a time where California was a Republican lock and the south was Democratic. But issues evolve, politics evolve, and electorates evolve. It’s a fascinating study.
I noted in another post that the Dems started this election with 242 EV’s in states that have gone Dem the last 5 presidential contests. It’s hard to argue that the candidate matters in these states, just the party.
Obama did turn some traditional GOP states into swingers in 2008 (IN and NC come to mind), but that seems to be the exception rather than the rule–obviously voting for the first black presidential candidate is an exceptional event. I agree with Dex that demographics rather than candidates have a far larger effect on voting; unless the candidate is an obvious exception (for good or ill), you can pretty much pick the swing states two years prior to the election.
More recently, I doubt many people in 2004 thought VA would become a bona fide swing state in 2008 & 2012. And demographics look like it’ll stay that way.