Santorum will win Louisiana primary, CBS News projects (CBS News) Rick Santorum will win the Louisiana primary Saturday, CBS News projects. The victory is fresh evidence of the weakness of front-runner Mitt Romney, who is nonetheless increasingly likely to be the Republican who takes on President Obama in November. According to exit polls, Santorum, a former Pennsylvania senator and social conservative, did well among evangelicals, Catholics and those who identify themselves as "very conservative." With 25 of 4,267 precincts reporting, Santorum had about 40 percent of the vote, while second place Romney had 31 percent. Former House Speaker Newt Gingrich was a distant third with 21 percent and Texas Rep. Ron Paul had just 5 percent of the counted vote. Santorum also did well among those who consider the economy the most important issue of the election. Among those voters, Santorum had 44 percent support, compared to 33 percent support for Romney, according to CBS News exit polls. The economy was considered the top factor among Republican voters in Louisiana Saturday. Romney, on the other hand, did well among those who say that defeating Mr. Obama is their top priority for choosing a candidate and those who identified themselves as moderates. For those who said electability was the most important factor in choosing a candidate, the former Massachusetts governor received 48 percent support, compared to 31 percent for Santorum. There were about 20 delegates at stake in Louisiana, but Santorum is not expected to claim all of them, even with his win. Going into the race Romney had around 550 of the 1,144 delegates needed to win, according to CBS News estimates. Santorum had more than 225 coming into tonight. Not counting Louisiana, Romney would need to win 45 percent of the remaining delegates while Santorum needs to win about 70 percent to win the nomination. Louisiana divides its delegates proportionally, so Romney could collect nearly as many delegates as Santorum, even with a loss. Gingrich has close to 130 delegates according to CBS News estimates after winning in just two states: South Carolina in January and his native Georgia earlier this month. Texas Rep. Ron Paul has not won any contests outright but has amassed more than 40 delegates. Voters in Wisconsin, Maryland and Washington, D.C., head to the polls on April 3, but Santorum is already looking to the April 24 contest in his home state of Pennsylvania, where more than 70 delegates are on the table. More than 200 delegates are at stake that Tuesday, including Connecticut, Delaware, New York and Rhode Island. None of the candidates appears to be dropping out anytime soon. While Romney is now on pace to garner enough delegates to win the nomination before the nominating convention in August, it remains possible that he finds himself short of the necessary delegates after the last primary in Utah at the end of June. That could lead to some of the so-called "unbound" delegates switching to Romney to unify the party, or it could lead to a contested convention. Santorum and the other candidates, of course, are hoping for the latter. On the stump, Santorum frequently calls on Republican voters not to nominate Romney, whom he calls moderate, reminding crowds that nominating incumbent President Gerald Ford, a moderate, in 1976 over the more conservative Ronald Reagan was a mistake. Ford lost to Jimmy Carter, a Democrat, who lost to Reagan four years later. Not coincidentally, 1976 was the last year there was a contested Republican nominating convention.