"The decision to get in or get out of a race is an extremely personal decision," said John Ryder, an RNC member from Tennessee who is neutral. "He's got to decide when he thinks it is no longer politically valuable to continue."
"It is very hard to see any path for Sen. Santorum to the nomination. It is very hard to see any path for Speaker Gingrich to the nomination," Ryder said. "But they and their supporters have to make that final call."
In the overall race for delegates, Romney has 660 and Santorum has 281, according to the AP count. Gingrich is even farther behind, with 135, followed by Paul with 51.
Romney has won 58 percent of the caucus and primary delegates so far. At that pace, he would reach the number of delegates needed to clinch the nomination — 1,144 — on June 5, when voters got to the polls in five states, including delegate rich California and New Jersey.
Santorum met privately Thursday with conservative activists to work on plans to stop Romney's march to the nomination. The group decided to pressure Gingrich to leave the race, believing that would help unite conservatives behind Santorum.
Gingrich, however, has already scaled back his campaign to the point that he schedules few public events. In the three primaries last Tuesday, all won by Romney, Gingrich got 11 percent of the vote in both Maryland and the District of Columbia and 6 percent in Wisconsin.
Even if Santorum had picked up every vote for Gingrich, Romney still would have won all three primaries.
"It's over with," said Bennett, the RNC member from Ohio. "And if Romney carries Pennsylvania, that completes it. He'll be the presumptive nominee before the end of the month."
Associated Press writers Brian Bakst in St. Paul, Minn.; Kantele Franko in Columbus, Ohio; Peter Jackson in Harrisburg, Pa.; and Will Weissert in Austin, Texas, contributed to this report.
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