Despite narrow primary wins in Alabama and Mississippi, Rick Santorum (Pa.) has fallen further behind in the delegate count to front-runner Mitt Romney, who won caucuses in Hawaii and American Samoa and captured about 30 percent of the vote in the two Southern states.

Because delegates are awarded proportionally in both Alabama and Mississippi, Romney won 23 delegates in those two states, compared to 31 for Santorum and 24 for former House Speaker Newt Gingrich (Georgia), according to the most recent projections by the Associated Press. But Romney captured 14 more delegates than Santorum in Hawaii and American Samoa, AP said, for a net gain of six delegates.

That allocation gives Romney 494 delegates, nearly twice as many as Santorum’s 251.

Still, Santorum’s victories--after being heavily outspent by Romney in both Southern states--bolster his claim to being the most viable conservative alternative to the former Massachusetts governor.

“We did it again. Who would have thought . . . that ordinary folks from across this country can defy the odds day in and day out?” Santorum, a former senator from Pennsylvania, exulted Tuesday night to cheering supporters in Lafayette, La., who will vote in their own primary March 24. “”

“The time is now for conservatives to pull together,” Santorum said. “The best chance to win this election is to nominate a conservative to go up against Barack Obama who can take him on on every issue.”

With Santorum and Gingrich remaining in the race, Romney has been able to exploit the split they have created among the most conservative Republicans, and to build a slow but steady lead in the contest for convention delegates.

At this point, it is almost mathematically impossible for any of Romney’s rivals to win the 1.144 delegates it will take to clinch the nomination. But they are holding on to the hope that by denying Romney that majority as well, they can take the fight into August and to the Republican National Convention in Tampa.

Romney--who has been dogged by losses in the more rural, conservative states--had played down his expectations in the South. But on Tuesday, he spoke dismissively of his closest competitor and portrayed himself as the inevitable nominee.

“Senator Santorum is at the desperate end of his campaign,” Romney said. “He’s far behind in the delegate count; he’s far behind in the popular-vote count . . . If you look at the math . . . it’s a very difficult road for him.”

Romney placed third behind Gingrich in both Alabama and Mississippi but won caucuses in Hawaii and American Samoa by large margins. Without a win Tuesday in what is essentially his home region, Gingrich may find it difficult to marshal the resources — and a rationale — to continue his campaign.

Gingrich has the best claim to being a Southerner: He spent part of his childhood in Georgia and represented the Atlanta area for decades in Congress. But he has won only two primaries, in Georgia and South Carolina, and is falling further behind the two leading contenders.

“This is pretty important,” said Rick Tyler, a longtime Gingrich aide who is now running a super PAC that has poured millions of independent expenditures into supporting the former speaker’s candidacy. “The PAC always felt we needed to win both of these states to change the narrative.”

Gingrich, however, gave no indication that he would end his bid. Instead, he grasped for a silver lining in the fact that Romney also fell short.

“The elite media’s effort to convince the nation that Mitt Romney is inevitable just collapsed,” Gingrich said Tuesday at a rally in Birmingham, Ala. “If you’re a front-runner and you keep coming in third, you’re not much of a front-runner.”

But Romney struggled as well — trying to prove he could make a strong showing in an electorate dominated by the GOP factions that have been the most hostile toward his candidacy. He essentially tied Gingrich in Alabama --winning 29 percent of the vote, compared to 29.3 percent for Gingrich and 34.5 percent for Santorum. In Mississippi, Santorum won 32.9 percent of the vote, Gingrich captured 31.3 percent and Romney got 30.3 percent.

In both states, Rep. Ron Paul (Tex.) ran far behind the three leading contenders.

At least eight in 10 voters in Mississippi and Alabama identified themselves in exit polls as evangelical Christians, a group that has been suspicious of Romney’s Mormon faith and of his past support for abortion rights.

Typically, Republicans anoint their nominee early. But this year has produced the most unpredictable and bitter fight in recent history, one that is pitting the establishment wing of the GOP against the insurgent forces of the tea party and social conservatives.

The races in Mississippi and Alabama picked up intensity after the mixed results of the March 6 Super Tuesday contests, which did not winnow the field as many had expected.

“Most people would have said a month ago it will be over by the time you get to Mississippi and Alabama,” said former senator Trent Lott (R-Miss.), a Romney supporter.

Romney’s supporters had hoped that he could put to rest questions about whether he can win over the party’s base.

Exit polls Tuesday suggested that electability was the foremost concern of voters in the two Southern states, as it had been in many of the earlier primaries. A plurality in both Mississippi and Alabama said the quality that mattered most to them in deciding which candidate to support was whether he can beat Obama.

But Santorum triumphed because just as many voters said that having a “strong moral character” or being a “true conservative” were the most important attributes. He won these voters by big margins.

Some Romney supporters suggested that Republican voters may be growing anxious to see this prolonged nominating contest come to an end, so that the nominee can begin marshaling an organization and financial support for the general-election contest.

“As the race progresses, the drumbeat gets louder and louder to get it over,” said Romney supporter Henry Barbour, a nephew of former Mississippi governor Haley Barbour and a Republican national committeeman.

Romney benefited from the muscle of the Mississippi political establishment. Nearly every Republican official elected statewide lined up behind him, including Gov. Phil Bryant, who gave Romney a late endorsement last week after initially backing the candidacy of Texas Gov. Rick Perry.

Henry Barbour’s younger brother Austin ran much of the Romney campaign’s ground operation in the state, and state auditor Stacey Pickering, who also has a surname famous in Mississippi Republican politics, was chairman of Romney’s campaign there.

Staff researcher Lucy Shackelford and polling manager Peyton Craighill contributed to this report.