Former Massachusetts Gov. Mitt Romney won the Illinois presidential primary Tuesday, expanding his lead in the race for the Republican nomination.

With 99 percent of precincts reporting, Romney captured 47 percent of the vote, according to the Chicago Tribune. Former Pennsylvania Sen. Rick Santorum trailed Romney, winning 35 percent of the statewide poll.

Also on the ballot, Rep. Ron Paul (R-Texas) received 9 percent of the vote and former House Speaker Newt Gingrich earned 8 percent, according to the Tribune.

Romney thanked supporters and volunteers in Schaumburg, Ill., late Tuesday night. Schaumburg and Evanston are both in Cook County, where the former Massachusetts governor captured 57 percent of the vote.

“Tonight we thank the people of Illinois for their vote and for this extraordinary victory,” Romney said. “Elections are about choices, and today, hundreds of thousands in Illinois have joined millions of people across the country to join our cause.”

After the 12-point loss, Santorum rallied a crowd in his home state of Pennsylvania, which will hold its primary next month.

“We’re going to win downstate, we’re going to win central Illinois, we’re going to win western Illinois,” Santorum said in Gettysburg, Pa. “We won the areas where conservatives and Republicans populate and we’re very happy about that.”

Romney padded his lead with huge margins in Cook, DuPage and other Chicago-area counties. However, Santorum led downstate, beating Romney in most southern and western counties.

More than a third of Republican primary voters in Illinois, considered a solidly Democratic state, described themselves as “moderate to liberal,” according to exit polls from the Associated Press. They favored Romney over Santorum by 19 percent.

As the primary season drags on, the race now shifts to Louisiana, where Santorum leads in recent polls. That contest will be held Saturday, followed by Maryland, Wisconsin and the District of Columbia in early April.