President Obama has had a bad streak in polls after doing pretty well against Mitt Romney in April, and Republicans are looking strong in Wisconsin and Nebraska.. Here's our guide to today's polls and why they matter.

Findings: Obama and Romney are tied with 45 percent of the vote.
Pollster: Gallup
Methodology: Tracking poll of about 3,050 voters polled over the last seven days. The margin of error is +/- 2 percentage points.
Why it matters: While Obama was polling ahead of Romney right as the Republican primary ended, May has been a pretty bad polling month for him, as the Talking Points Memo poll tracking chart shows below.
Caveat: Real Clear Politics' polling average has Obama up by 1.8 percentage points.


Findings: Wisconsin Gov. Scott Walker is leading Milwaukee mayor Tom Barrett in the recall election, with 50 percent to the Democratic challenger's 44 percent.
Pollster: Marquette Law School
Methodology: Survey of 704 registered Wisconsin voters from May 9 to May 12. The margin of error is +/- 4.1 percentage points.
Why it matters: The recall election will help one of the biggest fights in politics that got started last year -- whether the power of public sector unions should be limited. Outside groups are spending millions of dollars on ads on both sides. The candidates' support closely matches Walker's approval rating, which is 50 percent to 46 percent disapproving of his job performance. Walker is portraying the union law passed last year as an act of courage, and the poll shows that might be sticking a little. Seventy percent of independents think he's "decisive." 
Caveat: The vote is in just three weeks, though as the Nebraska Senate primary showed, these races can shift pretty quickly.


Findings: Nebraska state Sen. Deb Fischer was leading former Sen. Bob Kerrey 48 percent to 38 percent.
Pollster: Public Policy Polling
Methodology: Robo-calls to 1,028 Nebraska voters and 44 Republican primary voters from March 22 to March 25. The margin of error is +/- 4.7 percentage points.
Why it matters: This poll was taken a long time ago, when Fischer was polling a distant third in the Republican primary she won Tuesday night. But The New York Times' Nate Silver says that nevertheless, Democrats' chances of holding onto their majority in the Senate have improved. Nebraska Sen. Ben Nelson, a Democrat, is retiring, and Republicans think his seat will be one of the easiest to flip. Silver has moved Nebraska from the Likely Republican column to the Lean Republican column. He explains, "Mrs. Fisher should still be the favorite because of Nebraska’s strong Republican orientation, and she led Mr. Kerrey in polls in March. Still, the candidate-quality gap is substantial and could translate into her running an inferior campaign, and candidate quality is a variable that we have found to have predictive power in the past."
Caveat: Fischer's political peers in Nebraska suggest she's a pretty savvy lady.