santorum
Rick Santorum Tuesday ended his campaign for president. REUTERS

Rick Santorum ended his 2012 campaign for president on Tuesday, clearing the way for Mitt Romney to become the party's standard-bearer in November against U.S. President Barack Obama.

The former U.S. senator made his announcement at an event in Gettysburg, Pa., his home state. He said his daughter Bella's hospitalization over the weekend made him reassess his campaign.

We were very concerned about our role as being the best parents as we possibly could to our children, to make sure they had a country where the American dream is still possible, Santorum said, referring to himself and his wife, Karen. We made a decision over the weekend that while this presidential race is over for me, and we will suspend our campaign effective today, we are not done fighting.

No Endorsement Yet

Santorum's main rival for the GOP presidential nomination was never mentioned and the senator ducked reporters' questions about whether he will endorse Romney.

Romney, a former Massachusetts governor, congratulated Santorum on a campaign that finally emerged as the most credible threat to his landing the Republican nomination.

Senator Santorum is an able and worthy competitor, and I congratulate him on the campaign he ran, Romney said in the statement. He has proven himself to be an important voice in our party and in the nation.

Santorum's announcement comes after he suffered a string of defeats in last week's Wisconsin, Maryland and Washington, D.C., primaries. The possibility of losing Pennsylvania in its primary on April 24 may well have also fueled the decision, as many political insiders speculated Santorum's hopes for any future political career would be dashed if he did not win his home state.

Daughter Hospitalized Twice During Campaign

Then, his 3-year-old daughter, Bella, was hospitalized for the second time this campaign due to complications from the rare genetic disorder trisomy 18.

In Santorum's suspension of his campaign Tuesday, he recalled his improbable rise after he tied Romney in the Jan. 3 Iowa caucus, having spent much of the early campaign as an ignored, lower-tier candidate.

The result in Iowa -- revealed as a 34-vote victory after a recount -- prompted conservative Republicans and evangelicals to flock to his campaign as the main alternative to Romney, catapulting his campaign to front of the pack. He bested Romney in a series of primary contests in the South and Midwest.

This race was as improbable as any you will see as president, Santorum said. Against all odds, we won 11 states, millions of voters.

By suspending rather than ending his campaign, Santorum can still raise money and keep the delegates bound to him. He finishes his presidential bid with the second largest haul of delegates, 285.

Gingrich, Paul Press On

Meanwhile, the other two contenders still in the race -- Newt Gingrich, a former speaker of the House of Representatives, and Rep. Ron Paul of Texas -- are unfazed by Santorum's exit.

In a statement, Gingrich said he is in the race until the convention and made a pitch to Santorum supporters.

I am committed to staying in this race all the way to Tampa so that the conservative movement has a real choice, Gingrich said, according to the New York Times. I humbly ask Senator Santorum's supporters to visit Newt.org to review my conservative record and join us as we bring these values to Tampa.

Ron Paul's campaign also repleased a statement after Santorum exited the race. Congratulations to Senator Santorum on running such a spirited campaign. Dr. Paul is now the last -- and real -- conservative alternative to Mitt Romney, Paul's campaign said, in a statement. We plan to continue running hard, secure delegates, and press the fight for limited, constitutional government in Tampa.