SCHAUMBURG, Ill. — Front-runner Mitt Romney sailed to an easy victory in the Illinois primary Tuesday night, trumping Rick Santorum in yet another industrial state showdown and padding his already-formidable delegate lead in the race for the Republican presidential nomination.
"What a night," Romney told cheering supporters in suburban Chicago. Turning his attention past his GOP rivals, he said he had a simple message for President Barack Obama, the Democrat he hopes to face and defeat in November: "Enough. We've had enough."
Romney triumphed after benefitting from a crushing 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.
Returns from 47 percent of the state's precincts showed Romney gaining 50 percent of the vote compared to 33 percent for Santorum, 9 percent for Ron Paul and 7 percent for a fading Newt Gingrich.
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.
The primary capped a week in which the two campaigns seemed to be moving in opposition directions — Romney increasingly focused on the general election battle against Obama while Santorum struggled to escape self-created controversies.
Most recently, he 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.
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.
Romney's victory was worth at least 13 delegates.
That gave him 535 in the overall count maintained by The Associated Press, out of 1,144 needed to win the nomination. Santorum has 253 delegates, Gingrich 135 and Paul 50.
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.
A 10-day break follows before Washington, D.C., Maryland and Wisconsin hold primaries on April 3.
Santorum is not on the ballot in the nation's capital.
Private polling shows Romney with an advantage in Maryland, and Restore Our Future launched a television ad campaign in the state during the day at a cost of more than $450,000.
Wisconsin shapes up as the next big test between Romney and Santorum, an industrial state next door to Illinois, but one where Republican politics have been roiled recently by a controversy involving a recall battle against the governor and some GOP state senators who supported legislation that was bitterly opposed by labor unions.
Already, Restore Our future has put down more than $2 million in television advertising across Wisconsin. Santorum has spent about $50,000 to answer.
Neither Newt Gingrich nor Ron Paul campaigned extensively in Illinois.
Gingrich has faded into near-irrelevance in the race, but he was defiant in a statement issued after Romney sealed his victory.
"To defeat Barack Obama, Republicans can't nominate a candidate who relies on outspending his opponents 7-1. Instead, we need a nominee who offers powerful solutions that hold the president accountable for his failures," it said.