(CNN) -- Rick Santorum marches forward to the next GOP primary battle with wins in Alabama and Mississippi, throwing cold water on rival Mitt Romney's prediction that his campaign was reaching a "desperate end."
Romney, rejected again by Southern conservatives in the Tuesday primaries, was battling for second place with Newt Gingrich.
The latter had staked his campaign on a Southern strategy after winning South Carolina and Georgia.
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%. Gingrich was at 31%, Romney at 30% and Paul at 4%.
In another of Tuesday's races, Romney claimed victory in the caucuses of American Samoa, picking up the U.S. territory's nine delegates, according to local party officials. CNN also projects he will win the Hawaiian caucuses.
American territories play a significant part in the GOP presidential race in March.
Last Saturday, Romney won caucuses in Guam and the Northern Mariana Islands. He also picked up a majority of the delegates in the U.S. Virgin Islands.
The next contest on the GOP primary calendar is Puerto Rico on Sunday.
"We did it again," Santorum told supporters Tuesday night in Lafayette, Louisiana, which will hold a GOP primary on March 24.
Santorum, whose Alabama and Mississippi victories give him 10 wins to Romney's 18, poked at the frontrunner as he reiterated his stance that he is the viable conservative alternative to the former Massachusetts governor.
"People (said), 'You're being outspent (by Romney),' and everybody's talking about all the (delegate) math, and that his race is inevitable. Well, for someone who thinks this race is inevitable, (Romney) has spent a whole lot of money against me for being inevitable," Santorum told supporters.
Earlier in the day, Romney, who still holds a large overall delegate lead, said Santorum's campaign was trying to resuscitate a losing effort.
"Sen. Santorum is at the desperate end of his campaign and trying in some way to boost his prospects," Romney said on CNN's "The Situation Room."
As news was breaking of Santorum's win in Alabama, Santorum communications director Hogan Gridley replied to Romney's statement, saying, "It's just the beginning."
Santorum, a former senator from Pennsylvania, was coming off a big win in Kansas on Saturday and has given himself a bigger boost in the battle to be the conservative alternative to Romney by beating Gingrich in Alabama and Mississippi, in Gingrich's home turf in the South. The wins are somewhat of a surprise, because polls released Monday showed Santorum running 8 to 10 points behind Romney and Gingrich in the two states.
Still, because Alabama's 47 delegates and Mississippi's 37 delegates will be awarded proportionally, Romney appeared to maintain his delegate lead and may add to it after more moderate Hawaii's 17 delegates are distributed. A CNN delegate estimate early Wednesday showed Romney with a 489-234 lead over Santorum, giving him a 255-delegate margin.
The estimate had Gingrich at 139 delegates and Paul at 66. The number of delegates needed to clinch the nomination is 1,144.
Gingrich, speaking to supporters in Birmingham, Alabama, focused on the amount of votes that Romney didn't get, and said that "the elite media's effort to convince the nation that Mitt Romney is inevitable just collapsed."
"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. "And frankly, I do not 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 I've insisted in staying in this race."
Gingrich, who was under the most pressure to take both states, said he still had time to persuasively argue that he is the conservative who should go against President Barack Obama in the fall.
The former House speaker has won contests in South Carolina and Georgia, which he represented in Congress for two decades, but has finished third or worse in most contests outside the region and campaigned intensively in Alabama and Mississippi over the last week.
Romney's campaign has been holding up its large lead in delegates as a reason for Gingrich and Santorum to get out of the race. But Romney, who flew to New York on Tuesday ahead of a fundraiser and did not plan to address supporters Tuesday night, wouldn't have turned down a win in a region dominated by social conservatives, who have been hesitant to support his candidacy.
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."
Ari Fleischer, a White House press secretary under President George W. Bush, said, "There is no end in sight."
"I think the real impact ... tonight is that 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," Fleischer, a CNN contributor, said.
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 but Santorum will now travel there to try to make it harder for Romney.
Polls in Illinois, which votes on 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, a congressman from Texas, 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 Paul Steinhauser, Dana Bash, Rachel Streitfeld, Chris Welch and Joe Johns contributed to this report.
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