COLUMBIA, S.C. -- Trying to re-establish his place as a White House contender, U.S. Sen. Marco Rubio started unloading on nearly all of his fellow Republican candidates, declaring them unprepared for the national security responsibilities of the presidency.

Ted Cruz, meanwhile, said Donald Trump isn't conservative enough to be the GOP nominee. Jeb Bush's backers began painting John Kasich as weak on defense. Kasich maintained that he's a nice guy.

And Trump, the first-time candidate who leads them all, headed to Louisiana, which doesn't vote until March 5, two weeks after next-up South Carolina takes its shot at bringing order to this scrambled Republican race for president.

Republicans on Thursday felt out the best strategies to survive South Carolina and advance into the March primary schedule, when 58 percent of the party's delegate total will be at stake.

Specific to South Carolina, the overall statewide GOP winner will snag 29 out of 50 delegates, with the other 21 delegates are distributed evenly to the winners of the seven congressional districts.

Rubio, looking to re-establish his footing after a fifth-place finish in New Hampshire, lashed out at Trump, Cruz and Bush as he addressed retirees near the resort town of Hilton Head.

Rubio tried to embrace the GOP uncertainty Thursday, lashing out at Trump, Cruz and Bush on national security at a retiree community outside Hilton Head, S.C. He suggested that a nomination fight lasting through to the GOP's summer convention isn't a negative, ultimately leaving the delegates to argue over a nominee after they convene.

On real estate mogul Trump, Rubio declared: "Negotiating a hotel deal in another country is not foreign-policy experience."

Rubio also said that Bush, his former mentor in Florida politics, has no foreign-policy experience either. Rubio accused Cruz, a fellow first-term senator, of hurting U.S. military might with his budget stances.

In Sumter, S.C., Bush effectively called Trump a failure. The former Florida governor, himself once a commercial real estate executive, said he "didn't go bankrupt four times and call that success."

Bush cited his brother and father, both former presidents, as well, saying he embraces the "establishment" label. His campaign confirmed former President George W. Bush will campaign in South Carolina next week.

Kasich, the Ohio governor, continued his town-hall tour, pledging a positive campaign and alluding to continued efforts by the Bush campaign to label him as weak on defense.

"I'm worried about Jeb. It's all negative," Kasich said. "I'm going to keep doing what I'm doing. Either it will work or it won't."

Polls suggest Trump leads in South Carolina and nationally, with Cruz running second. Rubio banked on coming into South Carolina as the clear favorite for traditionalist Republicans wary over Trump and Cruz, creating effectively a three-man race going forward. Instead, he finished New Hampshire looking up at Kasich, the sitting Ohio governor, and at Bush, the former Florida governor.

Cruz is leaning heavily on religious and tea party conservatives, a sizable faction of the South Carolina primary electorate expected to top 700,000 voters, far outpacing Iowa and New Hampshire. Exit polls from Iowa and New Hampshire show Trump competed well with Cruz among voters who call themselves born-again Christians.

"You run first by energizing your base," said Cruz spokesman Catherine Frazier, confirming that while Cruz "will compete statewide" in South Carolina, he will concentrate his time in the upstate where religious conservatives are dominant. She confirmed Cruz will continue to highlight Trump's past, an allusion to his public support for abortion rights and same-sex marriage.

Bush and Kasich, meanwhile, are concentrating their early efforts along the South Carolina coast, which includes many transplants, veterans and active military members -- and which has trended in the past to more moderate candidates such as Mitt Romney, the GOP's 2012 nominee, and John McCain, the 2008 nominee.

Information for this article was contributed by Steve Peoples and Kathleen Ronayne of The Associated Press.

A Section on 02/12/2016