"Over the past few months, I've had the opportunity to speak with many of you about the problems you are facing in your businesses, in your households, and in your communities. You have encouraged me to carry your voice forward in 2014," he said in the statement. 

"With deep reflection, and strong support from you, Danielle and our kids, my family and friends, I wanted to share with you first that I've made the decision to step forward and run in 2014."

Dold's decision is a big boost for House Republicans — he's likely the only candidate who could make Illinois's 10th District competitive for the GOP. The one-term lawmaker lost to Schneider by 1 percentage point in a district President Obama carried with 58 percent of the vote.

The district had long remained in Republican hands; now-Sen. Mark KirkMark Steven KirkHigh stakes as Trump heads to Hill Five things to watch for at Trump-Senate GOP meeting Giffords, Scalise highlight party differences on guns MORE (R-Ill.) held it for nearly a decade before Dold won it in 2010. 

But Democrats made it slightly more Democratic in redistricting, and Dold couldn't hold on with Obama at the top of the ticket, despite running a very strong reelection campaign. 

In a midterm election where the Democratic base won't be as motivated, Dold could have a strong chance at winning back the seat.