One of the big surprises of the night on Tuesday was New York Mayor Michael Bloomberg's narrow re-election win.  Two theories seem to be making their way around to explain the near-defeat.  The first theory is that it was a backlash against his end-run around term limits.  The second theory is that it is just a bad year to be an incumbent.  Maybe if Congressman Anthony Weiner had run, some have surmised, he would have defeated Hizzoner.

I haven't seen exit polling, but when I saw a map of the returns by city council district, an alternate explanation immediately jumped out at me, probably because I spend way too much time staring at Congressional District maps.  I think its much more consistent with the facts then the other two theories I mentioned.  I'll explain all the markings I've drawn on the map in a second, but for now let's just look at reds and blues on the underlying map:

If what we were looking at was really a backlash against Bloomberg's removal of term limits, we would probably expect to see a dropoff in his performance in the more Republican portions of the district (since term limits is inexplicably a left-right issue, with conservatives supporting them).  But we don't see that -- Bloomberg did quite well on Staten Island, the bastion of conservatism in an otherwise liberal city.

Similarly, if what we were talking about was simply "a rough time to be governing," we would expect to see a more generalized depression in Bloomberg's performance.  But some areas really, really like Bloomberg, and some areas really, really don't like him.  The City was badly divided on election night.

Instead, I think this election was about, simply, race.  Although there wasn't much coverage of the election in the news media, Bloomberg's opponent was the City's African-American Comptroller, Bill Thompson.  The black lines on the map above show the city's Congressional districts -- which are often non-contiguous and horrendously gerrymandered to achieve racial balance in representation.

Those districts that send minority members to Congress are cross-hatched.  Notice the near-perfect overlap between the heavily white districts that still send white members to Congress and Bloomberg's performance in the underlying City Council districts.  Bloomberg prevailed among whites in upper-class Manhattan (look at the Upper East Side!), suburban Staten Island, and working class areas of Queens and Brooklyn.  Thompson did great among non-white voters.  Unless African-Americans in New York have a unique preference for term limits, I think this racial analysis is a far better, albeit more depressing, explanation.

Now would Congressman Weiner have turned his "T"-shaped Congressional district in the middle of the map (his district also encompasses a few non-contiguous areas in the Southwest of the map) blue while keeping the minority areas as strongly in his column as did Thompson?  Maybe, but I somehow doubt it.

We've made great progress in this country on the issue of race, but it still matters, a lot.  It nearly toppled a Mayor and potential President on Tuesday, and no one seemed to notice.