BOSTON — Even before the results were clear on Tuesday, Mitt Romney’s advisers conceded that they faced a steep climb to the nomination because of simple delegate math.
But now they also have to cope with a strong competitor to their momentum. Mr. Romney and his archrival for conservative voters, Mike Huckabee of Arkansas, each won at least five states on Tuesday. Mr. Huckabee lost narrowly in Missouri to Senator John McCain of Arizona.
Speaking to supporters on Tuesday night in suburban Little Rock, Ark., Mr. Huckabee, former governor of the state, derided the view that he was to be counted out, telling a modest-size crowd that the vote had indeed turned the Republican contest into a two-person race — and that he was in it.
“Tonight, we’re proving we’re still on our feet, and much to the amazement of many, we’re getting there,” he said to cheers.
He gave no indication that his still substantial delegate deficit was a reason for pulling out.
“As long as there are still votes and delegates, there’s going to be one guy answering the bell every time there’s a new round,” Mr. Huckabee told his supporters.
Though Mr. Huckabee lacks a convincing route to the nomination, his continued presence promises to make Mr. Romney’s path much more rugged, drawing away the very conservative voters Mr. Romney had counted on to defeat Mr. McCain.
Mr. Romney’s aides tried to minimize the Huckabee effect, saying it would simply delay his progress, not prohibit it.
“Huckabee has a specific appeal on specific issues to an important sliver of the electorate,” said Kevin Madden, a spokesman for Mr. Romney. “What Huckabee seems to be doing is still maintaining that specific appeal. What it’s done is it hasn’t stopped us. But instead it’s drawn out the primary calendar.”
Mr. Madden acknowledged that without Mr. Huckabee in the race, almost every previous nominating contest might have turned out differently.
“We’d have a greater ability to bring together these coalitions of conservatives, the economic and the social and the national security conservatives, and be the best candidate to unite the party,” Mr. Madden said.
Mr. Huckabee’s campaign manager, Chip Saltsman, said that the results on Tuesday had given the former Arkansas governor’s efforts a big boost and that contributions had increased.
“It gives us a lot of momentum, going forward,” Mr. Saltsman said. “I think we go forward with a lot more money than we thought we were going to have.”
He said Mr. Huckabee was not angling for second place on the Republican ticket.
“We’re still running for president,” Mr. Saltsman said. “We’re not running for vice president.”
As an example of the Romney campaign’s hurriedly revised calculations, aides had begun discussing an unlikely strategy that relies on delegates who are pledged to other candidates but who are not technically bound to them. Under that plan, the advisers envision that conservative fears continue to work against Mr. McCain, buying time and fueling a series of big victories for Mr. Romney. That would place him at a point where he has enough momentum to wrest some of the promised but not bound delegates into his column at a contested convention.
“Anybody who says it’s all going to be a mathematical exercise is wrong,” said Tom D. Rath, a senior adviser in the Romney campaign. “The math will follow the politics.”
The math, however, is daunting. Even some of the campaign’s more promising hypothetical delegate counts for how the race might shake out by Wednesday would leave them facing a serious deficit in the race to the 1,191 needed to clinch the nomination.
Under less rosy situations, Mr. Romney could be left with the almost impossible situation of having to win almost every remaining contest.
On the other hand, conservative grass-roots anger does appear to be building in some corners against Mr. McCain. Several conservative commentators have thrown their weight behind Mr. Romney.
On Tuesday, James C. Dobson, founder of Focus on the Family, released a blistering statement about Mr. McCain, saying he could not in good conscience vote for the senator.
Meanwhile, Mr. McCain has been playing up the names of conservatives who have endorsed him, including Senator Tom Coburn of Oklahoma, whom he called “the most conservative member of the Senate.”
Mr. Romney’s advisers hope the upshot of the grass-roots anger and a divided delegate picture is that they will be able to derail at least temporarily the rush to crown Mr. McCain as the nominee.
“The calendar gets spread out enough so you can compete everywhere,” said Ben Ginsberg, a senior adviser to Mr. Romney. “And the sort of rebellion that’s taking place in the grass roots against McCain has more time to take root.”