Mitt Romney's campaign tried to downplay the importance of the three state votes last week because no delegates were immediately awarded, but Republican voters don't appear to have bought the argument. Here's our guide to today's polls and which ones matter.

Findings: Mitt Romney and Rick Santorum are statistically tied nationally, with Romney getting 32 percent of Republican registered voters and Santorum getting 30 percent. Santorum has climbed 14 percentage points since February 7, when he won contests in Colorado, Minnesota, and Missouri.
Pollster: Gallup
Methodology:  Survey of 1,162 Republican and Republican-leaning registered voters from February 8 to February 12.
Why it matters: There have been a lot of surges in the 2012 Republican primary, but Gallup says this is the largest swing in five days. Pew Research Center also finds Santorum and Romney essentially tied, with 30 percent to 28 percent, respectively. National polls matter more now that a whole bunch of states will vote at the same time -- we'll soon see 18 elections in 15 days, NBC News' First Read writes.
Caveat: "It is too soon to say whether Romney's slim victory in Saturday's Maine caucuses (or his important symbolic victory in the Conservative Political Action Conference (CPAC) straw poll the same day) will advance his support, thereby stalling or reversing some of Santorum's recent gains," Gallup's Lydia Saad writes.

Findings: Santorum is beating Romney in Michigan 39 percent to 24 percent. That's in part due to Santorum's personal popularity (67 percent like him and just 23 percent don't.)
Pollster: Public Policy Polling
Methodology:  Robocalls to 404 Republican primary voters from February 10 to February 12.
Why it matters: Michigan and Arizona are the next states to vote (February 28). Arizona is winner-take-all, which means you can spend a lot of money and get nothing for it. But in Michigan, second place matters. Santorum has said that state is where his campaign is "planting our flag" even though Romney's father was governor of the state. The New York Times' Nate Silver now gives Santorum an 80 percent change of winning the state.
Caveat: PPP is a Democratic company.