Seems pretty clear to me the answer is yes. Overall, I doubt Clinton’s apparent margin would be as big as Obama’s is at this moment; I’d guess she’d be doing better in Florida and worse in Colorado and Virginia. I doubt with Clinton at the top of the ticket we’d be considering the possibility of a new Democratic Senator from Georgia or (less likely) Mississippi or Kentucky. It’s hard to imagine her bringing in as many first-time voters or turning as many independents. But by all indications, Hillary Clinton would be beating John McCain right now for the most important reasons Barack Obama is beating John McCain, and the main reasons (which got a huge exclamation mark from this fall’s economic news) it looked a year ago like Clinton/ Obama/ Edwards would beat Romney/ McCain/ Thompson: eight years of right-wing Republican rule has devastated the Republican brand (so much so that conservatives are left to plead that it wasn’t right-wing at all).
If Clinton had been the candidate, I bet McCain could have convinced some more folks that he was the one in the race who would “turn the page” on politics as usual in Washington, and he could have kept his money out of Georgia, but it’s hard to imagine he would be poised to win the election right now. Conversely, while Clinton’s claims about McCain as a nominee – that he would throw the kitchen sink at the Democrat – proved true, her claim that Obama as nominee would wilt under the attacks proved laughably false (though unsurprisingly, her own gutter attacks on Obama proved to have long life on John McCain’s shelf).
Point being, what a wasted opportunity it would have been if the months of competition between Obama and Clinton had been settled just based on who looked to more Democrats like a safer choice to go up against John McCain.