President Obama hasn't been cool on college campuses for months, so you could hardly expect young people to be excited to vote for the so-four-years-ago president. But poll numbers showing a 28 percentage point drop in enthusiasm among Democrats under 30 should alarm Obama's reelection campaign -- those youngsters helped him win in 2008, and they'd be the ones with the free time to volunteer in the fall. Here's our guide to today's polls and which ones matter.

Findings: Republicans are more exited to vote in 2012 than Democrats, but they're not nearly as psyched as Democrats were in 2008. 53 percent of Republicans are excited to vote, compared to 45 percent of Democrats. In 2008, 79 percent of Democrats were pumped. The group of Democrats with the biggest drop in enthusiasm is young folks: 76 percent of those 18 to 29 were excited four years ago, now just 48 percent are, a drop of 28 points.
Pollster: Gallup
Methodology: Telephone interviews with 1,014 adults nationwide from February 16 to February 19.
Why it matters: If they're not even excited to vote themselves, will young folks bother to try to convince their grandmas in Florida to vote for Obama? Republicans, meanwhile, experienced a dip in enthusiasm a couple months ago, but have bounced back. After being thrilled to vote in October 2011, Republican enthusiasm sunk to 49 percent in December, just 5 points above Democrats'. 
Caveat: "There is plenty of time between now and this November for voter enthusiasm to change, particularly once a GOP nominee is determined and the focus moves to the general election," Gallup says.

Findings: Nationally, Romney is suddenly way ahead of Santorum among Republicans, getting 40 percent to Santorum's 24 percent.
Pollster: Rasmussen
Methodology: Robo-calls to 1,000 likely Republican primary voters on February 29.
Why it matters: It's the first poll since Romney's victories in Michigan and Arizona. Earlier this month, Rasmussen found Santorum polling at 39 percent, Romney at 27 percent. As The Hill's Christian Heinze points out, when voters chose just between those two candidates, Romney crushes Santorum 50 percent to 38 percent. Michigan might have been Santorum's "last opportunity to deliver a knockout blow" to Romney, The New York Times' Nate Silver writes, because it "could have provided unambiguous evidence that the Republican electorate was rejecting him." Only a couple states, Illinois and Maryland, could come close to having the same "narrative consequences," Silver says.
Caveat: Rasmussen leans right.

Findings: Santorum's way ahead of Romney -- 40 percent to 19 percent -- in Tennessee. Gingrich has just 13 percent, and Paul has 11 percent.
Pollster: Middle Tennessee State University
Methodology: Telephone interviews of 646 Tennessee Republicans from February 13 to February 25.
Why it matters: Super Tuesday is Gingrich's last stand. He's said he must win neighboring Georgia. But he needs to do well in more than one state, obviously. Romney thinks he can at least get some delegates from those states -- he's campaigning there this weekend, ABC News reports.
Caveat: The poll was conducted before Romney won in Michigan and Arizona -- and even partly before the last primary debate.

Findings: Most Americans think colleges have a positive impact on the country, including most Republicans and the plurality of conservative Republicans. Conservatives are the most likely to think colleges have a negative impact, with 39 percent of them holding that view, but still, 46 percent think colleges better the nation. Among independents, 61 percent think colleges do some good.
Pollster: Pew Research Center
Methodology: Survey of 1,501 adults nationwide from February 8 to February 12.
Why it matters: Rick Santorum called President Obama a "snob" for saying all Americans should pursue at least a year of higher education. While the benefits of calling Democrats snooty have been known for years, being anti-college doesn't appear to be a winning strategy. That's probably why Santorum has suddenly started talking about all the post-grad degrees earned by his grandmother. Even so, he was booed at Belmont University Thursday, ABC News reports.
Caveat: Higher ed is not going to be a big issue in the election.