A CNN/ORC International poll showed about 60 percent of Republicans surveyed during the weekend think Gingrich, a former U.S. House speaker from Georgia, and Paul, a U.S. congressman from Texas, should end their campaigns for the GOP nomination. About the same percentage said Santorum, a former U.S. senator from Pennsylvania, should soldier on in his bid to overtake Republican front-runner Mitt Romney, a former Massachusetts governor.
CNN said it estimates Romney has 569 delegates in his corner, while Santorum has 262, Gingrich 136 and Paul 71. It will take 1,144 delegates to secure the GOP nomination.
Santorum, Gingrich and Paul have all said they are not quitting.
Santorum said Monday there are too many uncommitted delegates to concede Romney's nomination is inevitable.
"Gov. Romney is the front-runner but is a long way from a majority," Gingrich said Monday in Annapolis, Md.
"Why should we just throw in the towel because people like you say, 'Hey, throw in the towel?' " Paul asked.
The poll showed 36 percent of Republicans support Romney and 26 percent back Santorum for the nomination. In February, Santorum was up 34 percent to 32 percent, said CNN, which didn't provide a margin of error.
The poll found 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 percent for Romney and 30 percent for Santorum -- compared to the 10-point margin Romney currently has in the four-man field," CNN Polling Director Keating Holland said.
With the Wisconsin primary a week away, a poll by the Marquette Law School showed Romney leading Santorum in the state, with Paul and Gingrich trailing well behind.