DES MOINES, Iowa — With a nationally focused campaign that leans on strong debate performances and television advertising, Marco Rubio isn’t going all out in any one of the early voting states.

That’s raised eyebrows among Republicans in states such as Iowa, where people are used to being lavished with attention in a presidential campaign.

As 2015 wanes, the Florida senator is back in Iowa on Tuesday for a multi-day swing, hoping to shore up support and finish in the top tier of candidates in the Feb. 1 caucuses.

But he is continuing to spread his time and money across the early states, showing no indication he will choose just one to make his mark.

That’s unlike Texas Sen. Ted Cruz, who has set his sights on Iowa, and former Florida Gov. Jeb Bush, who is pushing hard in New Hampshire.

While supporters say Rubio just needs to stay in the top cluster in the first few states, some see the approach as risky.

“The caucuses are about organize, organize, organize and get hot at the end,” said Iowa Republican strategist Doug Gross, who has not endorsed a candidate. But as for Rubio and his people, “I think they’ve intentionally tried to run a different campaign.”

In another early voting state, South Carolina, former Republican Party chair Karen Floyd described Rubio’s approach as “curious,” saying his organization there has not been as visible as several of his rivals.

Rubio spokesman Alex Conant said the campaign has no plans to “give up on states we can win.”

But it is risky to be seen as having to win a particular state a month before the voting, he said. “We see four states where Marco can succeed,” Conant said, referring to the four earliest ones — Iowa, New Hampshire, South Carolina and Nevada.

In Iowa, recent polls have found Cruz and Donald Trump battling for first, with Rubio usually a distant third. He’s seen as competing most directly with others considered part of the GOP establishment — Bush, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich.

Most agree he doesn’t actually need to win the caucuses, but must emerge as the leader of that group.

“As 2016 starts, Iowa feels it’s Cruz’s to lose,” said Matt Strawn, a former Iowa Republican Party chairman. “A lot of Senator Rubio’s success will be determined by whether he can blunt the momentum or not allow any of his New Hampshire competitors to build momentum.”