As the 2014 midterm elections draw closer, an avalanche of polling data will emerge on the key races that will decide who controls the House of Representatives, the Senate, and statehouses across the country. What follows is a brief summary of some key polls from the week of March 23:

Wisconsin

Wisconsin governor Scott Walker is holding on to his lead over Democratic challenger Mary Burke, according to the latest Marquette University poll.

The poll finds Walker with a 48 to 41 percent lead, slightly up from his 6-point advantage in January. Despite his solid lead, however, Walker’s approval rating has dropped a net 9 percent since Marquette’s previous poll; it now stands at 47 percent, with 47 percent disapproving.

Burke’s numbers still have plenty of room to grow; she is viewed favorably by 19 percent and unfavorably by 22 percent, with 59 percent unsure or saying that they don’t know enough about her to form an opinion. By contrast, Walker is known to all but 5 percent of the state.

Marquette’s poll tracks closely to The Huffington Post’s polling average of the race, which has Walker leading Burke 48 to 41 percent.

Georgia

Former Reebok CEO David Perdue has climbed into the lead in Georgia’s crowded Republican Senate primary, according to a Landmark/Rosetta Stone poll released Wednesday.

Perdue heads the field with 21 percent, followed by U.S. Reps. Paul Broun and Jack Kingston at 15 percent, Rep. Phil Gingrey at 13 percent, and former Georgia Secretary of State Karen Handel at 10 percent.

The wealthy businessman’s advantage in the survey has pushed him into the lead in The Huffington Post’s polling average for the first time (although Broun, Kingston, and Gingrey all remain within striking distance).

If no candidate wins over 50 percent in the May 20 primary — which seems almost certain — then the top two finishers will compete in a runoff election on July 22. Republicans would likely prefer to see Perdue and Kingston in the top two, rather than the gaffe-prone Broun or Gingrey.

The Republican nominee will face Democrat Michelle Nunn in the general election, which arguably represents the Democrats’ best opportunity to win a Republican seat in 2014.

Iowa

It has not been a good week for Rep. Bruce Braley (D-IA), the Democratic candidate to replace retiring Iowa senator Tom Harkin. First, video emerged of Braley criticizing the state’s Republican senator Chuck Grassley for being “farmer from Iowa, who never went to law school,” and thus unfit to chair the Senate Judiciary Committee — a potentially serious gaffe in rural Iowa.

Now a new poll suggests that his lead over his Republican rivals is narrowing. Rassmussen’s first survey of the race finds Braley with just 3 percent leads over top rivals Mark Jacobs and Joni Ernst, and a 4 percent lead over Matt Whitaker.

Braley shouldn’t panic yet, however; other polls give him a much stronger edge over his Republican rivals.

Virginia

Republicans are on a serious losing streak in Virginia, and it doesn’t look like it will stop in November.

According to a Quinnipiac poll released Thursday, Democratic incumbent Mark Warner is walloping likely Republican opponent Ed Gillespie 46 to 31 percent in Virginia’s upcoming Senate election.

That 15-point lead is right in line with the polling average, which shows Warner up 46 to 30 percent.

Quinnipiac finds that Warner is quite popular within the commonwealth; voters approve of his job performance by a 55 to 33 percent margin, and they say he deserves re-election by 49 to 36 percent.

Making matters worse for Gillespie, the Virginia GOP’s unsuccessful 2013 campaigns have left it pretty much broke; the party has less than $70,000 in cash on hand, according to The Washington Post.

Photo: Gage Skidmore via Flickr