Personnally my money would be on the Gallup and Rassmussen models.
"......There's no question that President Obama's 2008 campaign, which focused on turning out new low-propensity voters in minority communities, helped inflate nonwhite voters' influence in the electorate. In Virginia alone, the nonwhite share of the electorate spiked from 21 percent in 2006 to 30 percent just two years later, a virtually unprecedented leap. The question is how many of those voters come back to the polls in 2012.
Republicans and Democrats alike believe the African-American vote is unlikely to change between 2008 and 2012. But they differ dramatically on the number of Hispanic voters who will show up at the polls—a key factor in critical battleground states like Colorado and Nevada. Republicans believe turnout will be down, depressed by Obama's failure to pursue immigration reform during his first term. Democrats think the booming number of Hispanic residents means their share of the electorate will only increase.
The same argument applies to younger voters. In 2008, 18 percent of the electorate was made up of voters between 18 and 29 years old. That's higher than the percentage has been in recent presidential years, when the youth vote has made up around 15 or 16 percent. Republicans believe the younger share of the electorate will slide slightly, and that Obama will win fewer of those voters anyway.
The manifestation of these disagreements is evident in polling weights. Most Republican pollsters are using something close to a 2008 turnout model, with the same percentage of white, black, and Hispanic voters as the electorate that first elected Obama. Most Democratic pollsters are a little more bullish on minority turnout, which helps explain some of the difference between the two sides......"