Steven Senne, AP
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SCHAUMBURG, Ill. — Mitt Romney took a major stride toward the Republican presidential nomination Tuesday night, routing Rick Santorum in the Illinois primary for his third big-state win in a row and padding his already-formidable lead in the race for convention delegates.
"What a night," Romney exulted to cheering supporters in suburban Chicago. Looking beyond his GOP rivals, he said he had a simple message for President Barack Obama, the man Republicans hope to defeat next fall: "Enough. We've had enough."
Returns from 98 percent of Illinois' precincts showed Romney gaining 47 percent of the vote compared to 35 percent for Santorum, 9 percent for Ron Paul and 8 percent for a fading Newt Gingrich.
That was a far more substantial showing for Romney than the grudging victories he eked out in the previous few weeks in Michigan and Ohio, primaries that did as much to raise questions about his ability to attract Republican support as to quell those questions.
Santorum, who hopes to rebound in next Saturday's Louisiana primary, sounded like anything but a defeated contender as he spoke to supporters in Gettysburg, Pa. He said he had outpolled Romney in downstate Illinois and the areas "that conservatives and Republicans populate. We're very happy about that and we're happy about the delegates we're going to get, too."
"Saddle up, like (Ronald) Reagan did in the cowboy movies," he urged his backers.
Romney triumphed in Illinois after benefiting from a crushing, 7-1 advantage in the television advertising wars, and as his chief rival struggled to overcome self-imposed political wounds in the marathon race to pick an opponent to Obama.
Most recently, Santorum backpedaled after saying on Monday that the economy wasn't the main issue of the campaign. "Occasionally you say some things where you wish you had a do-over," he said later.
Over the weekend, he was humbled in the Puerto Rico primary after saying that to qualify for statehood the island commonwealth should adopt English as an official language.
Romney's victory was worth at least 41 delegates in Illinois, while Santorum won 10. The two rivals were battling for the final three delegates but the results were too close to call on election night.
Romney has 563 in the overall count maintained by The Associated Press, out of 1,144 needed to win the nomination. Santorum has 263 delegates, Gingrich 135 and Paul 50.
Exit polls showed Romney preferred by primary goers who said the economy was the top issue in the campaign, and overwhelmingly favored by those who said an ability to defeat Obama was the quality they most wanted in a nominee.
He won among votes who said they were somewhat conservative or moderate, while Santorum prevailed among those who said they were "very conservative."
While pre-primary polls taken several days ago in Illinois suggested a close race, Romney and Restore Our future, a super Pac that backs him, unleashed a barrage of campaign ads to erode Santorum's standing. One ad accused the former Pennsylvania senator of changing his principles while serving in Congress, while two others criticized him for voting to raise the debt limit, raise his own pay as a lawmaker and side with former Sen. Hillary Rodham Clinton to support legislation allowing felons the right to vote.
In all, Romney and Restore Our Future outspent Santorum and a super PAC that backs him by $3.5 million to $500,000, an advantage of 7-1.
In the long and grinding campaign, Santorum looked to rebound in next Saturday's primary in Louisiana, particularly given Romney's demonstrated difficulties winning in contests across the Deep South.
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