GETTYSBURG, Pa. — Bowing to the inevitable after an improbably resilient run for the White House, Rick Santorum quit the presidential race on Tuesday, clearing the way for Mitt Romney to claim the Republican nomination.

“We made a decision over the weekend, that while this presidential race for us is over, for me, and we will suspend our campaign today, we are not done fighting,” he said.

Santorum, appearing with his family, told supporters that the battle to defeat President Barack Obama would go on but pointedly made no mention or endorsement of Romney, whom he had derided as an unworthy standard-bearer for the GOP.

The former Pennsylvania senator stressed that he’d taken his presidential bid farther than anyone expected, calling his campaign “as improbable as any race that you will ever see for president.”

“Against all odds,” he said, “we won 11 states, millions of voters, millions of votes.”

The delegate totals told the tale of Santorum’s demise. Romney has more than twice as many delegates as Santorum and is on pace to reach the 1,144 delegates needed to clinch the nomination by early June. Still in the race, but not considered a factor: former House Speaker Newt Gingrich and Texas Rep. Ron Paul.

Santorum had hoped to keep his campaign going through the Pennsylvania primary on April 24, but decided to fold after his severely ill 3-year-old daughter, Bella, spent the weekend in the hospital.

He said that while Romney was accumulating more delegates, “we were winning in a very different way. We were touching hearts” with a conservative message.

In a statement, Romney called Santorum “an able and worthy competitor.” With Romney on his way to the nomination and a contest against the president, Obama’s campaign manager, Jim Messina, sharply criticized Romney for waging a negative ad campaign against his opponents.

“It’s no surprise that Mitt Romney finally was able to grind down his opponents under an avalanche of negative ads. But neither he nor his special interest allies will be able to buy the presidency with their negative attacks,” Messina said. “The more the American people see of Mitt Romney, the less they like him and the less they trust him.”

Santorum said the campaign had been “a love affair for me, going from state to state. … We were raising issues, frankly, that a lot of people did not want raised.”