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Chip Somodevilla; Scott Olson/Getty Images

Illinois was the only state to cast its votes in the Republican presidential primary on Tuesday, but the political watching didn't end there. Further down the ballot, the state also voted in a host of hotly contested congressional races, including a high-profile challenge between incumbent Jesse Jackson Jr. and former U.S. Rep. Debbie Halvorson.

On the GOP presidential-primary front, Mitt Romney won as expected (polls earlier in the day showed him with a whopping 15-point lead against first runner-up Rick Santorum). No matter what happened, Romney would have remained ahead in the delegate count, so the bigger triumph for the former Massachusetts governor lies in improving the perception of his campaign.

With the decisive win -- 48 percent of the vote at the time major networks called the race -- he not only widened his delegate lead but also struck a blow against Santorum's momentum over the past month. In fact, in his victory speech Romney made the scantest of references to his Republican opponents ("I'd like to congratulate my fellow candidates on a hard-fought contest here") and zeroed in on the man he considers to be his real competition: President Barack Obama.

"After years of too many apologies and not enough jobs, historic drops in income and historic highs in gas prices, a president who doesn't hesitate to use all the means necessary to force through Obamacare on the American public but leads from behind in the world, it's time to say this word," Romney said to electrified supporters. "Enough."

In the attention-grabbing race for Jesse Jackson Jr.'s Chicago district, which he has represented since 1995, the son of the famed civil rights activist won against his challenger, also following a sizable advantage in recent polls. Even though Jackson defended his seat beneath the cloud of a House Ethics Committee investigation into allegations that he improperly tried to influence then-Illinois Gov. Rod Blagojevich's 2008 Senate appointment, and despite the fact that redistricting significantly reduced the African-American influence in his district, he still sailed to a big win. Jackson is now considered a safe bet to win in November.

Cynthia Gordy is The Root's Washington reporter.