WEST DES MOINES, Iowa >> A nagging problem hovers over Sen. Marco Rubio of Florida as he crisscrosses the country seeking support in the states with the first four nominating contests: With a month and a half until the voting begins, he still has not committed himself fully to trying to win any of them.

That hedged, wait-and-see approach served Rubio well until recently, as he floated to the top tier of national polls, won the backing of influential financiers and began drawing hundreds to his rallies. His aides, flouting age-old political wisdom, started suggesting that he might not even need to win Iowa or New Hampshire — that a second- or third-place finish could be enough.

But as the primary fight becomes fiercer, and Rubio’s closest competitors start zeroing in on a single, must-win contest — like Iowa for Sen. Ted Cruz of Texas and New Hampshire for Gov. Chris Christie of New Jersey — Rubio’s all-things-to-all-people strategy is stretching his campaign thin, posing challenges in focusing his message and raising doubts among his supporters about his seriousness.

Some Rubio backers in the first four states to vote — Iowa, New Hampshire, South Carolina and Nevada — are voicing concern about whether Rubio is leaving voters there with the impression that he does not need them to win. And some of Rubio’s own aides are now arguing privately that they should do more to push back against the belief that he is running an indifferent campaign before it becomes too widespread.

“The campaign efforts for Marco Rubio in Iowa can very easily be perceived as wanting to place in the top three in the caucus and not necessarily to win,” said Kenney Linhart, a pastor in Des Moines who is supporting the Rubio campaign. Regardless of how serious Rubio is about trying to win the state, Linhart added, the belief that he is not is harmful: “Perception is as powerful as intent or will.”

Most recent polls put Rubio in third place in Iowa, behind Donald J. Trump and Cruz. Though he is not in the lead in any of the states that vote first, he generally finds himself in the top three or four.

Indeed, Rubio’s light footprint in Iowa has been the talk of the state’s political community for months. He was unable to hire a local operative to run his campaign there, and instead brought in an Arkansas-based Republican strategist, Clint Reed, in September to oversee his Iowa campaign. And Rubio is relying on 31-year-old Eric Teetsel, who lives in Kansas, to handle outreach to social conservatives and evangelicals — rankling some Iowans used to a more neighborly outreach.

Inexperience and inattention to detail on the ground can have a tangible cost. Melody Slater is a former Lee County chairwoman for the now-defunct presidential campaign of Gov. Scott Walker of Wisconsin. Shortly after Walker dropped out, Rubio’s campaign announced that Slater was one of several of Walker’s backers who had signed on with them.

But now she says she is having second thoughts. “I had three campaigns call me that day — Huckabee, Cruz and Rubio,” Slater said in an interview, explaining that she agreed to endorse Rubio only at his campaign’s request. She said she still liked Rubio and may indeed caucus for him.

But she cautioned that she was also drawn to Cruz’s Christian values.

“You’ve got to be careful about what you say, don’t you?” Slater mused.

From the Rubio campaign’s perspective, not putting a marker down yet in any state means not having to set expectations that might not be met. His advisers do not want to face the possibility of fading in a state they said they could win. And they have told supporters and donors that Jeb Bush’s surprisingly lackluster campaign left them with more time to make their move.

“We’re doing things differently,” said Bobby Kauffman, a Republican state senator in Iowa who is helping the Rubio campaign. “People don’t like things being done differently.”

In the meantime, they are relying on a robust digital outreach program in the early-voting states and using local and national television to increase Rubio’s visibility. When he campaigns, he tends to eschew small towns and venues for larger population centers and media markets.

“Exposure is Marco’s friend,” said his pollster, Whit Ayers. “And exposure is the enemy of a whole lot of the rest of these candidates.”

Campaign advisers readily dismiss as superficial the older quantifiable signs of seriousness about Iowa’s tradition-bound caucuses, like lining up endorsements in all 99 counties or dotting the state with campaign offices. They refused even to divulge the number of staff members on the campaign’s payroll in Iowa, dismissing such details as the preoccupation of obsessives in the news media and on rival campaigns.

Yet, if Rubio’s campaign styles itself as more attuned to a modern media age when more voters can be reached through Facebook and Fox News, there are plenty of people who prefer being wooed as if it were still a landline and postage-stamp era.

Rubio is not likely to decide where to make his move until sometime next month. His schedule this week — both in his public rallies and private meetings — shows what a broad appeal he is trying to make: After sitting down with billionaire casino magnate Sheldon Adelson in Las Vegas before Tuesday night’s debate, Rubio set off for Iowa where he continued his efforts to woo evangelical Christian voters. He will visit New Hampshire next and then South Carolina.

Every Republican nominee in modern times has won either Iowa or New Hampshire at a minimum. But until now, at least, Rubio’s strategy has pointed toward a test of whether a candidate who finishes no better than second in either could still manage to stay alive.

It is a risky gambit: Opponents are already attacking Rubio in New Hampshire for taking a lackadaisical approach there. And The New Hampshire Union Leader, an influential newspaper in the state, which has endorsed Christie, accused Rubio of “just going through the motions” in his visits to the state.

Presidential campaigns struggle every cycle with the question of how many resources to commit to states they stand little chance of winning, and the consequences are not always straightforward.

In 2008, Sen. John McCain of Arizona spent relatively little time campaigning in Iowa, and watched his poll numbers plummet, but then came back to win in New Hampshire and capture the Republican nomination. In 2012, Mitt Romney’s campaign agonized over whether to compete in Iowa, only to decide right before Thanksgiving in 2011 — a little more than a month before the caucuses — that he would.

“Spreading your forces out over a wide front would make me very nervous,” said Stuart Stevens, Romney’s chief strategist in 2012. “Every day in a campaign is ‘Sophie’s Choice,’” he added. “And that’s the hardest thing. You’ve got to decide where you’re going to live and where you’re going to die.”

The question of where Rubio can get a victory that will provide his campaign with the early bounce it needs to prove he is able to win the nomination is coming up more and more as he travels the country. When he ventured an answer recently in West Des Moines, he did not display much interest in entertaining what he clearly considered an abstract question at this point.

“I’m not a psychic,” he said, adding that he was confident in his strategy. “We want to do well. We want to do very well. And hopefully that means winning.”

© 2015 The New York Times Company