As Rick Santorum's slipped a little in Ohio, he's slipped a lot nationally. And while he and Mitt Romney continue to tear each other down, they're not hurting President Obama -- he's polling even with an unnamed Republican candidate in Georgia. Here's our guide to today's polls and which ones matter:

Findings: Romney is ahead of Santorum nationally by 16 points -- 38 percent to 22 percent. Way way back in ancient history (February 20), Santorum led Romney nationally by 10 points.
Pollster: Gallup
Methodology: Interviews of 1,211 Republican and Republican-leaning registered voters from February 29 to March 4.
Why it matters: Newt Gingrich was called a "double Lazarus" for his multiple comebacks, but Romney's managed to beat back every candidate who briefly polled ahead of him. Maybe Romney should be called a "double Lazarus" or a "triple Lazarus" or a "Lazarus times 11." If Santorum doesn't win in states where he's favored Tuesday, like Ohio, and he doesn't have the lead nationally, what's his argument for staying in the race?
Caveat: An NBC News/ Wall Street Journal poll has Romney only 6 points up. Plus, Romney's started doing more town halls, which means more chances to talk unscripted -- which means more chances to mention firing people and Nascar team-owning pals.

Findings: Romney and Santorum are tied among all Ohio primary voters with 32 percent. Santorum has no advantage among Catholic Ohioans, getting 33 percent of their support to Romney's 39 percent. Voting begins in mere hours!
Pollster: CNN/ ORC
Methodology: Survey of 1,825 registered voters in Ohio, among them 546 likely Republican voters, over the last day and a half.
Why it matters: Santorum is trying really hard to win the popular vote in Ohio -- it's a big swing state with lots of blue-collar voters, who should be his people. 
Caveat: A couple other polls released today show Romney a point or two above Santorum. "We’re winning," Santorum told ABC News' Jonathan Karl. "Whether we end up with the most votes or not [in Ohio], we’re winning." If he said it, it must mean it's true. (That is a joke, for the record.) As for Santorum's standing among Catholics, Romney's advantage "is within the sampling error," CNN reports.

Findings: President Obama verses Generic Republican is tied, 48 percent to 48 percent, in Georgia
Pollster: CNN/ ORC
Methodology: Survey of 1,778 registered voters in Georgia, among them 527 likely Republican voters, over the last day and a half.
Why it matters: Georgia has long been a red state, but its demographics are changing -- more middle class black people are moving back to the South, and the Latino population is growing. Even so, John McCain beat Obama in Georgia by 5 percentage points in 2008. Four years earlier, George W. Bush beat John Kerry by almost 17 points.
Caveat: Georgia probably will not be a swing state once the general campaign gets going. Still, this result could have something to do with how the Republican primary has hurt the party. The NBC/ Journal poll shows a large majority associate negative words with the primary -- words like "discouraged," "lesser of two evils," "painful," "poor choices,"and "underwhelmed." And 40 percent say the primary had given them a more unfavorable view of the GOP.