Do Democrats have a turnout problem when Obama is not on the ballot?

The results from Tuesday’s election in Wisconsin continued a troubling pattern for Democrats: some of their base isn’t as excited about other Democrats as they are President Obama.

Exit polls from Wisconsin showed a sizable drop in the youth vote from 2008. And Milwaukee Mayor Tom Barrett, the Democratic candidate, won the 18-29 year-old vote by four points, compared to the 29-point margin of Obama in 2008.

For a variety of reasons, it’s very difficult to compare a recall election to a presidential contest. And the drop-off in the youth vote likely came in part because the college semester just ended, and some would-be young voters are back in their home states or more disengaged from the political process.

But this is not the first time this drop-off has occurred. Democrats lost the House in 2010 in part because older, white voters turned out heavily for Republicans, while young voters in particular didn’t go the polls. And some of this pattern even predates Obama, as young voters turned out heavily in 2004, but dropped off two years later.

Perhaps helped by campaigning in the state by Jesse Jackson and Al Sharpton, black turnout in the recall in Wisconsin was similar to 2008.

But the Wisconsin results, paired with those from the 2010 midterms, show a broader challenge for Democrats. Increasingly, Democrats are the party of young, secular white voters and minorities, while Republicans rely on an older, largely white political base. If Democrats can’t count on the young voters to show up if Obama is not on the ballot, it could cause major challenges in mid-term elections and gubernatorial contests in particular.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr