By this time tomorrow, somebody might be writing his concession speech. However, it might not be the presidential loser's last foray into politics, especially if the president is on the short end of the decision. The Gray Lady seems to think this is Obama's last race, win or lose. I'm not so sure
If he wins, I could easily see a 55-year-old Obama going off to Harvard or the University of Chicago to teach law and/or poli-sci or take on some UN post. We've yet to see a two-term ex-president get into politics after leaving the White House, although he might take a hankering to a possible Supreme Court slot a la Taft, assuming his successor was a Democrat (heaven help us).
If he loses, he might well be Grover Cleveland and set his sights on a 2016 rematch with Romney; he'd be a tough out in a primary.