Sen. Ted Cruz, a Republican from Texas, said Friday that he plans to stay out of primaries involving GOP senators. (Mike Fuentes/Bloomberg)

It only took some brief remarks for Sen. Ted Cruz (R-Tex.) to widen the growing divide between himself and his Senate Republican colleagues.

Cruz told reporters here Friday that he plans to stay out of primaries involving GOP senators, a move that means the upper chamber’s top two Republicans will not have the public support of one of the most popular figures on the political right, as they each seek to fend off conservative challenges. It’s a decision that carries risks for Cruz’s long-term standing in the party, observers and Republican strategists say, but is likely to satisfy his most ardent supporters.

“The reason is simple,” Cruz explained after declining to endorse Senate Minority Whip John Cornyn (R-Tex.) or any other incumbent. “I think every elected official, including me, owes it to the people, owes it the grass roots, to go and make the case to the grass roots why he or she is representing their interests.”

Cornyn has not drawn any top conservative challengers, but his inner circle is taking the threat of a strong primary challenge seriously. Cornyn responded that he agrees with Cruz that “the only endorsements that matter are those of the Texas voters.” But Cruz’s reluctance to back his colleague threatens to harden the conservative resistance Cornyn has encountered.

Even beyond Texas, Cruz’s silence could embolden conservative activists and groups that boosted him to an unlikely 2012 win to press on against GOP incumbents. In Kentucky, the Club For Growth and the Senate Conservatives Fund, two groups that supported Cruz, are considering whether to back the primary challenger of Senate Minority Leader Mitch McConnell. A handful of other Senate incumbents are also facing some pressure from the political right.

“It’s going to alienate many current senators and establishment Republicans,” Rice University political scientist Mark Jones said of Cruz’s posture. “But I think he’s already decided that bridge is burnt and he’s not going to try to reconstruct it.”

For Cruz — who has stoked talk about a White House bid by traveling to the early nominating states, releasing his birth certificate and promising to renounce whatever right he has to Canadian citizenship amid questions about whether being born in Canada precludes him from being president — stoking tensions with Republican leaders could prove perilous in the long run. Mounting a successful presidential campaign has required cultivating relationships with party leaders, history has shown.

“There is a risk” in what Cruz is doing, said longtime Texas Republican strategist Bill Miller, who once worked for Cornyn. “The way that the game is played is that if you’re not going to help people in their elections, which are the most intense experiences politicians have in their lives, then you can expect that if you ask for a favor, don’t expect it to be returned.”

Cruz’s rhetoric and actions suggest that he thinks he can build a national following by eschewing the traditional routes to power and emphasizing his loyalty to the most conservative elements of the party.

Bill Smith, 58, of Atkinson, N.H., attended Cruz’s speech at a fundraiser here and liked what he saw. “I’d go to the wall for him as an activist,” Smith said.

“I don’t think Cruz has anything to worry about,” said conservative strategist Keith Appell. “The more he does things like this, the larger the reservoir of support and good will grow” in his political base.

Despite his preference for catering to those outside of Washington, Cruz must work within its bounds now, and his navigation of Senate races could cause confusion about where he stands and about where other Senate Republicans come down, too.

As vice chairman of the National Republican Senatorial Committee, Cruz is in a very visible position when it comes to Senate races. In an interview with The Washington Post, he warned the organization not to endorse in primaries even as he said he may do so on an individual basis. And while Cruz says he is not supporting any incumbents, a review of campaign finance documents revealed that his leadership political action committee gave money to Cornyn and a handful of other Republican senators.

The NRSC has lauded Cruz’s contribution to the committee. But in time, he could complicate its work. Cruz says his focus is on picking up Democratic-held seats. Picking sides in Republican primaries in those races would instantly prompt questions about where the NRSC stands.

On his first trip to New Hampshire as senator, Cruz was warmly received by a crowd of donors and activists eager to hear him speak. But even the friendly confines of the gathering exposed Cruz’s struggles in the Senate.

Introducing Cruz was Sen. Kelly Ayotte (R-N.H.). As Cruz did, she explained to the crowd the perils of President Obama’s signature health-care law. But she does not support a plan endorsed by Cruz to defund the Affordable Care Act by refusing to support any appropriations or continuing resolution bills that devote even a penny to its funding. Cruz has traveled the country in August trying to build support for the proposal, but it has found almost no new traction in the Senate, where the majority of Republicans are not on board with the idea. Cruz acknowledged the difficulty of his task toward the end of his speech.

“We cannot win this fight if the ordinary rules of Washington apply,” he told the crowd.

Paul Kane contributed to this report.