RIck Santorum and Mitt Romney are polling so close in Michigan that some are predicting a Bush vs. Gore situation, with one winning the popular vote and the other winning the most delegates. Santorum's women problem spreads to Ohio, and President Obama gets more popular. Here's our guide to today's polls and why they matter.

Findings: Romney's moved about 2 percentage points ahead of Santorum in Michigan, which votes February 28.
Pollster: Rasmussen, Public Policy Polling
Methodology: Robo-calls to 750 likely Republican voters on February 26; robo-calls to 421 likely Republican voters on February 26.
Why it matters: A little over a week ago, Santorum was polling almost 10 points ahead of Romney. But Romney's negative attacks and Santorum's poor debate performance appear to have hurt him.
Caveat: A poll, also conducted February 26, from Mitchell Research/ Rosetta Stone finds Santorum 2 percentage points ahead of Romney. The New York Times' Nate Silver calls the state "a true toss-up." In another sign of how close the vote might be, a Romney-backing official in the state tells BuzzFeed Romney could win the most delegates but lose the popular vote.

Findings: Santorum is ahead of Romney in Ohio, which votes March 6, with 36 percent to his 29 percent. Santorum faces a gender gap: Men like Santorum 38 percent to 25 percent, but among women, the candidates are essentially tied.
Pollster: Quinnipiac
Methodology: Survey of 847 likely Republican primary voters in the state from February 23 to February 26.
Why it matters: Initially it seemed like Santorum was not facing the gender gap many predicted would follow his focus on social issues like abortion and contraception. Nationally, Republican women like Santorum better now than they did in January, according to a Washington Post poll. But in states where the candidates are campaigning, like Michigan and Ohio, it's a different story.
Caveat: How the candidates do in the February 28 votes will probably have a significant impact on their standing in places that vote later.

Findings: Obama's approval rating is 53 percent, and he's beating both Romney and Santorum by double digits.
Pollster: Politico/ George Washington University
Methodology: Survey of 1,000 registered likely voters from February 19 to February 22. 
Why it matters: Since December, Obama's approval rating has slowly climbed out of the mid-40s above 50 percent. That helps explain why so many Republicans are worried they could lose the 2012 election even with the weak economy.
Caveat: A Gallup poll shows Romney and Obama tied. Real Clear Politics' poll average shows shows a smaller portion of the electorate approving of the president.

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Elspeth Reeve