In getting this far, Rick Santorum has achieved what no one — with the possible exception of himself — would have thought was possible four months ago. But the very qualities that made him a contender are turning into problems, as he is more frequently being tripped up by saying what is on his mind and by sometimes-errant tactical instincts.

His candid comments and unconventional moves were badges of authenticity in the early contests, but they now raise doubts about Santorum’s capacity to be his party’s standard-bearer in the general election. And they have hampered Santorum’s ability to capi­tal­ize on opportunities to narrow the gap with Mitt Romney, particularly in large states with diverse electorates.

His second-place showing in Illinois represented another squandered opportunity for Santorum, who is running out of chances to stop Romney and can’t afford to spend more time backtracking on things he’s said. As in Michigan and Ohio, Santorum had come within striking distance only to fall short.

Santorum prides himself on the fact that he is an unscripted candidate who will answer whatever he is asked. He has even gone so far as to declare that “when you run for president of the United States, it should be illegal to read off a teleprompter, because all you’re doing is reading someone else’s words to people.”

In Santorum’s case, however, even his admirers think that might not be such a bad thing to try, at least every now and then.

“What he says is undistilled Rick Santorum, and sometimes he says things inartfully,” said Richard Land, the political leader of the Southern Baptist Convention, who has not endorsed a candidate. “I hope that in the near future Rick will get some really good wordsmiths and give some better speeches.”

Speaking off the cuff has proven treacherous for Santorum, undercutting his efforts to expand his base of support beyond social conservatives to economically stressed voters who might be able to relate to the former senator’s blue-collar roots.

“He is going to answer the question, which is a good thing,” said his spokesman Hogan Gidley. “But it’s something we lament sometimes.”

In fact, it can sometimes seem that Santorum swings at every ball that’s pitched. On Tuesday, for instance, he criticized President Obama for allowing his 13-year-old daughter, Malia, to take a spring break trip to Mexico, parts of which the State Department has deemed unsafe.

“If the administration is saying that it’s not safe to have people down there, then just because you can send 25 Secret Service agents doesn’t mean you should do it,” Santorum said on a conservative talk radio show. “And when the government is saying this is not safe, then you don’t set the example by sending your kids down there.”

However, there is no State Department warning for Oaxaca, where she reportedly is.

One prominent Republican who is close to Santorum and who spoke on condition of anonymity, said the candidate also suffers from having honed his reflexes in the U.S. Capitol: “The problem is, he’s a former senator, and he wants to litigate every point.”

During the past few days alone, Santorum has strayed off message into the subject of pornography, one that normally does not figure in presidential contests.

In response to what he said was an inquiry from a voter, Santorum posted on his Web site an accusation that the Obama administration had “turned a blind eye to those who wish to preserve our culture from the scourge of pornography.” He vowed to crack down on hard-core porn if he is elected.

Santorum also had to mop up after his statement that “I don’t care what the unemployment rate is going to be. It doesn’t matter to me.”

When front-runner Romney — predictably — leapt on that comment to suggest that his chief rival was giving short shrift to a subject that is at the top of voters’ concerns, Santorum was forced to clarify: “Of course I care about the unemployment rate. I want the unemployment rate to go down, but I’m saying my candidacy doesn’t hinge on whether the unemployment rate goes up and down.”

Santorum has yet to fully tamp down the doubts about whether his personal opposition to contraception might affect his approach to policy in an area of law that has been settled for decades.

So defensive is Santorum’s team on the subject that his wife, Karen, felt compelled to declare to CNN’s Piers Morgan: “Women have nothing to fear when it comes to contraceptives; he will do nothing on that issue.”

Those who have observed Santorum’s political career are not surprised at what some would call his frankness — and what others see as a lack of discipline.

“About a month ago, the off-message, visceral, provocative Santorum emerged, and I was frankly stunned that it took so long for that to happen. It’s just who he is,” said G. Terry Madonna, director of the Center for Politics and Public Affairs at Franklin and Marshall College in Lancaster, Pa.

The core of Santorum’s campaign operation has expanded little since its lean days in Iowa. His closest advisers include his wife, longtime strategist John Brabender, his former Senate chief of staff Mark Rodgers and political consultant Chuck Laudner, in whose pickup truck Santorum logged countless miles across Iowa.

A more recent addition is John Yob, who was brought aboard the campaign to track convention delegates.

In a conference call with reporters on Tuesday, Yob argued that the candidate has actually earned more delegates than has generally been credited in the media.

It’s going to be “difficult for any candidate to get a majority prior to the national convention,” Yob said, adding that if it ends up going to a floor fight, “we view that as favorable territory for Rick Santorum because the delegates to the convention will by and large be more conservative.”

That, however, has not happened in the Republican Party since 1948, when it took three ballots for New York Gov. Thomas Dewey to secure the nomination.

Given how outgunned he is in organization and financial resources, Santorum has little margin for error. One good sign: In February, he raised $9 million, which put him not far behind the $11.5 million taken in by Romney.

And he has hopes of winning Saturday’s Louisiana primary, as well as his home state of Pennsylvania in April and Texas after that. Yob also said Santorum is well positioned for a round of primaries in May, which will include several Southern states.

Yet some of the candidate’s decisions — such as spending time and money in Puerto Rico, where he had virtually no chance of picking up any delegates in Sunday’s primary — have been mystifying. And Santorum made his chances there even worse by asserting that the island’s residents would have to make English their “main language” before becoming a state.

Supporters hope, however, that he will get points for that in the long run.

“His willingness to answer that question the way he did is a sign he did not pander to that audience,” said social conservative leader and former presidential contender Gary Bauer, who has endorsed Santorum.