Washington (CNN) -- With calls increasing for some or all of them to drop out, challengers to Republican presidential front-runner Mitt Romney say they intend to keep battling until the nomination gets settled.
A CNN/ORC International poll released Tuesday indicated that most Republicans would like to see former House Speaker Newt Gingrich and Texas Rep. Ron Paul end their bids, but they also want conservative challenger Rick Santorum to stay in the race.
The poll, conducted over the weekend, showed that about six in 10 Republicans want Gingrich and Paul to halt their campaigns, while a similar number supported Santorum continuing his bid.
According to CNN's latest estimate, Romney has secured 569 delegates and needs 575 more to reach the 1,144 required to clinch the GOP nomination.
Santorum, the former Pennsylvania senator, has 262 delegates, with Gingrich at 136 and Paul at 71.
Despite the long odds, none of the three trailing candidates appears close to giving up.
Santorum challenged the delegate math, telling CNN's Wolf Blitzer on Monday that the Republican race was likely to continue until the party's national convention in August in Florida.
"There may be someone with what they say are enough delegates, but as you also know, Wolf, a huge number of delegates are uncommitted," Santorum said. "They may be for me, or they may be for Mitt, but they're technically uncommitted, and therefore you can't put them in your column."
Gingrich said Tuesday that he would drop out if Romney, the former Massachusetts governor, reaches the 1,144-delegate threshold to claim the nomination. However, Gingrich added he doubted that would happen before the convention.
"Gov. Romney is the front-runner but is a long way from a majority," Gingrich said at Maryland's capitol building in Annapolis. "If (Romney) does get, by the time Utah votes on the 26th of June, if he gets a majority, obviously I will support him and will be delighted to do anything I can to help defeat Barack Obama."
Otherwise, Gingrich said, a failure by Romney to secure the nomination in the primaries would bring "one of the most interesting open conventions in American history."
"It'll be a 60-day dialogue on television, radio, the Internet all the way up to Tampa," Gingrich said. "And the question will be asked: Who can best beat Barack Obama? And at that point, I think, most Republicans agree that I would probably do a better job debating Obama than any other candidate. And I think it becomes a very viable, very lively campaign."
Paul also sounded committed to staying in the race, telling CNN's "Piers Morgan Tonight" on Monday that "it's way too soon for you to write anybody off."
"Why should we just throw in the towel because people like you say, 'Hey, throw in the towel'? " Paul asked.
According to the new poll, 36% of Republicans support Romney for the nomination, and 26% back Santorum. It was a different story in February, when the two men were effectively tied in CNN's last national survey, with Santorum at 34% and Romney at 32%.
The survey seemed to dispel the commonly held notion that Gingrich and Santorum were vying for conservative support against the more moderate Romney. According to the poll, most of Gingrich's supporters said Romney was their second choice, rather than Santorum.
"If you recalculate the GOP horse race using the Gingrich voters' second choice, Romney's lead over Santorum grows to 15 percentage points -- 45% for Romney and 30% for Santorum -- compared to the 10-point margin Romney currently has in the four-man field," CNN Polling Director Keating Holland said.
The primary calendar resumes April 3 with contests in Wisconsin, Maryland and the District of Columbia. A three-week break follows until April 24, when New York, Pennsylvania, Delaware, Connecticut and Rhode Island vote.
Those contests in more moderate states in the Northeast, Mid Atlantic and Midwest appear to favor Romney over Santorum, with the possible exception of Pennsylvania, which Santorum represented in Congress for nearly two decades.
On Tuesday, a week before the Wisconsin primary, a new poll by the Marquette Law School showed Romney leading Santorum, with Paul and Gingrich well back in the contest for 42 delegates.
CNN's Gabriella Schwarz, Shawna Shepherd, Kevin Liptak and Shannon Travis contributed to this report.