Editor's note: Sound off on the campaign here
(CNN) -- Rick Santorum took his re-energized Republican presidential campaign to Puerto Rico on Wednesday after key primary victories in the South that raised questions about conservative rival Newt Gingrich's viability as a candidate and portended a long battle with frontrunner Mitt Romney.
Romney, rejected again by Southern conservatives in the Tuesday primaries in Mississippi and Alabama, won caucuses in Hawaii and American Samoa to claim about a third of the total delegates available and maintain his lead.
However, Santorum's twin primary triumphs -- while narrow -- reframed the GOP race as a one-on-one battle between the socially conservative former Pennsylvania senator and the more moderate Romney, with Gingrich's chances fading fast.
Texas Rep. Ron Paul, the libertarian champion, continued to trail well behind the other three candidates in the campaign to face President Barack Obama in November.
"There is no end in sight," noted Ari Fleischer, a CNN contributor who was White House press secretary under President George W. Bush. "... For Republicans who thought that maybe Mitt Romney could come South and make this race look like it was coming to an end, this race is going on and on and on."
Santorum headed to Puerto Rico on Wednesday ahead of Sunday's primary there, which is a day after caucuses in Missouri and two days before a showdown with Romney in the Illinois primary.
"We did it again," Santorum told supporters Tuesday night in Lafayette, Louisiana, which will hold another Southern primary March 24.
The Alabama and Mississippi victories give Santorum 10 states so far to Romney's 18, and he poked at the frontrunner on Wednesday as he reiterated his stance that he is the viable conservative alternative to the former Massachusetts governor.
"It's pretty sad when all you have is to do math instead of trying to go out there and win it on substance and win it on what Americans want to hear about," Santorum told CNN in reference to Romney's claim of an insurmountable lead in delegates. "We're a long, long way from over."
Romney said Wednesday in an interview on Fox that his lead so far in the campaign shows he has support across the Republican spectrum, adding that "some who are very conservative may not be yet in my camp, but they will be when I become the nominee when I face Barack Obama."
He also noted Santorum called him a "real conservative" in endorsing his candidacy in 2008, "so obviously when campaigns get tough and you get towards the end of this process and you are way behind in delegates you say some things which may be contradictory to what you said only four years ago."
Earlier Wednesday, Romney received the endorsement of former Pennsylvania Gov. Tom Ridge, who was the first homeland security secretary when the department was created in the Bush administration after the September 11, 2001, terrorist attacks.
"I've met accomplished and strong leaders in my life," Ridge said in a statement released by Romney's campaign. "Mitt Romney is one of them."
Gingrich, who based his campaign on a Southern strategy after winning South Carolina and Georgia, appeared to be in major trouble after losing both Dixie primaries Tuesday.
Last week, Gingrich spokesman R.C. Hammond said the former speaker had to win Alabama and Mississippi in order to remain credible. Gingrich later said he would continue to the national convention in Tampa no matter what happens, and he repeated that assertion Tuesday night.
"The fact is that in both states, the conservative candidates got nearly 70% of the vote, and if you're the frontrunner and you keep coming in third, you're not much of a frontrunner," Gingrich said of Romney's performance in Mississippi and Alabama.
Citing what he called Romney's vulnerabilities on health care reform, Gingrich said he doesn't "believe that a Massachusetts moderate who created Romneycare as the forerunner of Obamneycare is going to be in a position to win any debates this fall," and that is part of the reason he's "insisted in staying in this race."
Calls for Gingrich to drop out and unite conservative support for Santorum have already started, but Gingrich argues that none of the candidates are likely to reach the 1,144 delegates necessary to clinch the nomination before May or June at the earliest, and probably not until the August convention.
CNN's estimated delegate count Wednesday had Romney at 498, with Santorum at 239, Gingrich at 139 and Paul at 69.
Prior to Tuesday, Romney needed to win roughly 48% of the remaining delegates to win, while Santorum needed about 66% and Gingrich needed 72%. Santorum, Romney, and Gingrich each won roughly a third of the combined delegates at stake in Mississippi and Alabama.
In Alabama, Santorum won 35% of the vote. Gingrich and Romney both had 29% -- although Gingrich was about 2,000 votes ahead with 99% of the vote counted -- and Ron Paul had 5%.
With 99% of the vote counted in Mississippi, Santorum had 33% to 31% for Gingrich, 30% for Romney and 4% for Paul.
Romney's victories in Hawaii and American Samoa demonstrated his stronger organization. Last Saturday, Romney won caucuses in Guam and the Northern Mariana Islands, and he also picked up a majority of the delegates in the U.S. Virgin Islands.
Santorum was coming off a big win in Kansas on Saturday, and his victories Tuesday indicated a comeback after trailing Gingrich and Romney in polls released Monday.
Romney's campaign has pointed to its large lead in delegates as a reason for Gingrich and Santorum to get out of the race.
Eric Fehrnstrom, a Romney campaign senior adviser, said the campaign met its goal of taking roughly one-third of the Mississippi and Alabama delegates.
"Once the dust clears, you'll be able to look and see that there really will be no ground that our opponents have made up against Mitt Romney," Fehrnstrom said Tuesday night. "And as you look at the upcoming contests on the calendar, there are no opportunities for them to have significant wins that allow them to accumulate large numbers of delegates so that they can close that gap with Mitt Romney."
Exit polls from Alabama and Mississippi show that Romney still has some ground to make up to win over conservatives: In Alabama, 55% of those polled said Romney's position on the issues wasn't conservative enough; in Mississippi, the number was 49%.
In another trend that has continued throughout the campaign, more voters saw Romney as the best choice for defeating Obama in the general election.
In Alabama, 46% saw Romney as being the most likely to beat Obama, while both Santorum and Gingrich were the favorites of 24%; in Mississippi, 50% of those polled saw Romney as having the best chance of beating Obama, compared to 24% for Gingrich and 23% for Santorum.
As results were coming in Tuesday night, CNN chief political analyst Gloria Borger said that hardcore conservatives' persistent preference for Santorum or Gingrich means Romney benefits from the presence of both.
"Gov. Romney needs Rick Santorum and Newt Gingrich right now. ... If it weren't for them splitting the conservatives -- the very conservative, the evangelical, the tea party voters -- Mitt Romney would not be within sort of a position to win in either of Mississippi or Alabama. So the fact that they're splitting the vote ... he ought to pay them both to stay in for a little bit longer."
Santorum and Romney are expected to split the next few contests on the calendar. Santorum won the nonbinding primary in Missouri in February and is expected to take the state's caucuses on Saturday. Romney is expected to win Puerto Rico's primary on Sunday.
Polls in Illinois, which votes Tuesday, show a tight race and Santorum is expected to win in Louisiana a week from Saturday.
Then the race turns north and eastward -- the District of Columbia, Maryland and Wisconsin vote on April 3 and Romney is the early favorite there. But that's three weeks away and much has changed in such a span in the most volatile Republican race in generations.
Paul didn't campaign over the past week in either Alabama or Mississippi. Both states held open primaries, which meant Republicans, independent voters and Democrats could cast ballots in the GOP contests.
CNN's Jim Acosta, Paul Steinhauser, Peter Hamby, Alan Silverleib, Dana Bash, Rachel Streitfeld, Chris Welch and Joe Johns contributed to this report.
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