Obama would have lost in many climates, but so would many other candidates. Winning the Presidency is as much about timing as anything else. Reagan won in 1980 because the country was so fed up with the failures of big government and the economic/inflationary/foreign policy crises. He wouldn't have won in 1968 or 1976 (opinion), because America was not ready for a staunch conservative. Obama wouldn't have won in almost any other year, but then again he wasn't running in any other year. He was a phenomenal candidate, because he is the most liberal president in our nations history and won by a large margin. America is a center-right nation, and the fact that he won cannot be overstated.
As far as McGovern, he was a terrible candidate ideologically, but he was much like Obama in his ability to get the youth vote and energize the left. After all, he was seen as the outsider candidate by most in the party going into 1972. He had to defeat three establishment candidates (Muskie, Humphrey, Scoop) to win the nomination, and he did. That takes a lot. However he was simply the wrong candidate in the wrong place at the wrong time.
McGovern actually was an outsider candidate, unlike Obama.
Obama losing to McCain in 2008 would have been like Reagan losing to Carter in 1980, and Obama was well on his way to doing so.
