Republican front-runner Mitt Romney said he's going to win his party's presidential nomination in a slow but sure accumulation of delegates.
On Wednesday, he prodded his challengers to drop out of the race.
Romney's campaign issued a memo that showed the former Massachusetts governor with a substantial mathematical lead that could not be challenged by any other candidate.
"As Gov. Romney's opponents attempt to ignore the basic principles of math, the only person's odds of winning they are increasing are President Barack Obama's," it said.
Romney said it would take an act of God for anyone else to beat him at this point. At the present pace, he expects to secure the nomination in June.
Former Sen. Rick Santorum, R-Pa., rejected Romney's offer.
"What won't they resort to, to try to bully their way through this race?" he said in Lenexa, Kan. "If the governor now thinks he's ordained by God to win, then let's just have it out."
Meanwhile, a Santorum supporter urged former House Speaker Newt Gingrich, R-Ga., to abandon his quest for the nomination.
Gingrich said he would consider it if he thought Santorum would beat Romney and then President Barack Obama.
"I don't," he added.
A candidate needs 1,144 delegates to secure the Republican nomination. Current delegate totals as follows:
- Romney - 415
- Santorum - 176
- Gingrich - 105.
The GOP marathon continues with primaries in Alabama and Mississippi on Tuesday, March 13.