But Maher will have a tough time trying to defeat Kline, who's not a top Democratic target and is expected to cruise to a seventh term.
The liberal host announced the "winning loser” during a live broadcast of HBO's "Real Time with Bill Maher" in Washington DC.
Maher targeted Kline, chairman of the House Education and Workforce Committee, for voting to repeal ObamaCare 54 times, his stance against gay marriage and denying climate change funding.
"He's one of those silent threats you never see coming....Ebola. ISIS. John Kline," he said. "He embodies the sellouts that keep this town running."
The finalist in the challenge, which targeted Republicans in somewhat competitive districts around the nation, included Republican Reps. Mike Coffman (Colo.), Renee Ellmers (N.C.) and Blake Farenthold (Texas).
Maher will now campaign against Kline in an attempt to unseat the Minnesota Republican and flip his district from red to blue, hoping the lawmaker will "feel the heat" from his constituents.
Kline may represent a swing suburban Twin Cities district — which did narrowly vote twice for President Obama — but Democrats have never managed to recruit a top challenger. This year, he faces a rematch against former state Rep. Mike Obermueller (DFL), who he beat in 2012 by eight points in a good year for Democrats.
"There are a lot of terrible, entrenched congressmen out there," he said in a statement posted on his show's website. "Many don’t even have an opponent. We’re going to choose one of them, throw him into the national spotlight, and see if we can’t send him scuttling under the refrigerator on Election Night."
Immediately after his show's taping, the 58-year-old jetted to a D.C. theater five minutes away for a live hour-long stand-up special.
This post was updated at 10:41 p.m.