Rep. Joe Walsh (R-Ill.). (Manuel Balce Ceneta/AP)

That’s why The 5 in 5 Project has come to the outskirts of the Windy City for the next two days to see how Democratic challengers to Republican incumbents are faring in must-win races.

Today, we're tracking the race between Rep. Joe Walsh (R-Ill.) and his Democratic challenger, Tammy Duckworth, an Iraq war veteran and former Veterans Affairs official. The contest in recent weeks has turned nasty as Walsh, a freshman tea party-backed lawmaker, continues to direct personal attacks at Duckworth, a popular figure among Democrats and liberal activists who has enjoyed a large national following ever since becoming one of the first Iraq war veterans to run for Congress.

During the 2006 election cycle, then-Sen. Barack Obama and then-Rep. Rahm Emanuel convinced Duckworth to run for Congress and despite broad support from the party establishment, she lost the race.

Walsh, who has a propensity to make outlandish, headline-grabbing comments, earned attention again this week for recent comments he made at a town hall meeting where he suggested that radical Islam is a “real threat” to the United States and has come to the suburbs of Chicago. The remarks sparked outrage and criticism from local members of the the Council on American-Islamic Relations and Duckworth also called Walsh’s statement irresponsible.

But in a video message posted Wednesday, Walsh said that even the Obama administration agreed that radical Islam is a problem and has severed ties to CAIR.

“Bowing down to political correctness has — and will — get Americans killed,” Walsh said in the video. “We must always speak truth to this threat, no matter how politically incorrect. Yet Tammy Duckworth agrees with CAIR when she calls me irresponsible. Tammy, what exactly did I say that you disagree with? Yes or no, do you agree with the Obama administration that there is a home-grown threat that exists from the radical strain of Islam?”

Walsh’s direct statement to Duckworth (watch the video to hear and see his tone when he says her name) is just the latest in a series of comments he’s made about her.

Most notably, Walsh last month suggested that Duckworth speaks too often about losing her legs during a helicopter accident in Iraq. He compared Duckworth to Sen. John McCain (R-Ariz.), who Walsh claimed is reluctant to discuss his military service and years in captivity.

“He talked a little bit about it, but it was very uncomfortable for him. That’s what’s so noble about our heroes,” Walsh said. “Now I’m running against a woman who, I mean, my God, that’s all she talks about. Our true heroes, the men and women who served us, it’s the last thing in the world they talk about.”

Days later in a raucous CNN interview, Walsh insisted: “I don’t regret anything I said.”

Walsh’s comments paid dividends for Duckworth, who told me recently that Walsh’s comments triggered a ten-fold increase in traffic to her campaign Web site and a new wave of volunteers and donations from across the country.

“And a lot of it came from veterans who were upset,” Duckworth said of the donations. (More of my interview will be posted later today.)

Walsh also endured a stumble in mid-June when famed Eagles guitarist Joe Walsh endorsed Duckworth, allowing her campaign to joke that “Joe Walsh supports Tammy Duckworth.” The endorsement was partially payback for the lawmaker’s decision to borrow a song by the rocker and change the lyrics — a move that the musician later mocked.

As with most congressional campaigns, there is little reliable polling at this stage of the race. But it promises to be a nasty one — and one that Democrats must win if they hope to win back the House majority — however slim those chances now seem.

Make sure to read 5in5 highlights from Monday, Tuesday and Wednesday and track Ed’s trip at or on Twitter, Facebook and Instagram.