WASHINGTON (AP) — Out on the presidential campaign trail, Sens. Marco Rubio and Ted Cruz are rising in the polls. Back in the Senate, their ambitions can sometimes be a nuisance for fellow lawmakers, including vulnerable Republicans up for re-election next year.

The latest example: Rubio and Cruz are pushing for the Senate to go farther than the House when it takes up legislation to repeal President Barack Obama's health care law. They want to make good on promises to repeal "Obamacare" in its entirety, rather than a more targeted repeal approved recently by the House.

But other Senate Republicans are resisting their push, objecting in particular to trying to repeal the health law's Medicaid expansion. A number of Senate Republicans represent states where Medicaid was expanded under the law to provide coverage to more of the lowest-income residents.

"I don't want to see it included and I've been making my pitch for a couple weeks so we'll see. I'm not alone," Republican Sen. Shelley Moore Capito of West Virginia said this past week of the Medicaid expansion. Noting that millions could lose coverage, she said: "If we don't have a replacement vehicle for that, that's a problem for me."

And as for the impact of presidential politics on the issue, Capito said: "You know obviously I think that's playing into it."

Other states that would be impacted by repealing the health law's Medicaid expansion include Ohio, New Hampshire, Pennsylvania and Illinois, all represented by Republican senators facing tough re-election fights next year in presidential battleground states targeted by Democrats.

But Cruz, of Texas, and Rubio, of Florida, are sticking by their joint stance even as they butt heads on the campaign trail over immigration. "If this bill cannot be amended so that it fully repeals Obamacare pursuant to Senate rules, we cannot support this bill," they said in a joint statement last month, along with another conservative senator, Mike Lee of Utah.

The dispute is just one example of how senators running for president and those seeking re-election can have different goals. Cruz, in particular, has aggravated fellow senators who believe he's used the Senate to promote his political ambitions, and unlike Rubio, he's grown isolated in the Senate as a result. Republican Sen. Kelly Ayotte of New Hampshire, who is in a competitive re-election fight, released a public letter to him earlier this year demanding to know his "strategy for success" as he pushed to deny funding to Planned Parenthood even if it risked a government shutdown.

"You have senators running to be the nominee of the Republican Party, and you have senators who are running to win re-election in the general election in the fall of 2016, and those at the moment are fundamentally different priorities," said Brian Walsh, a Republican consultant. "And that's reflected in how they are approaching legislation today."

GOP Sen. Rand Paul of Kentucky, another candidate for president, infuriated colleagues earlier in the year when he single-handedly forced a temporary lapse in the Patriot Act, enacted to assist law enforcement and the intelligence community in coping with extremist threats against the U.S., and issued fundraising appeals to highlight his stance.

GOP Sen. Roger Wicker of Mississippi, who leads the Senate GOP's campaign committee, downplayed any division between presidential candidates and vulnerable Senate Republicans.

"That wouldn't be unusual, would it?" he observed. "There are some people in some states who see it one way, and some who see it the other."

For Wicker and Senate Majority Leader Mitch McConnell of Kentucky, the primary focus is not on the presidential campaign but on making sure Democrats cannot pick up the four or five seats they need to retake the Senate in next year's elections.

There are five highly vulnerable Republican incumbents in the Senate, and any piece of legislation must be weighed by GOP leadership for how it would affect them, whereas for Rubio, Cruz or Paul, the focus at the moment is on Republican primary voters.

The health law repeal bill would be considered under special Senate rules that would protect it from a Democratic filibuster and allow it to get to Obama's desk. The president would be certain to veto it, but Republicans would view that in itself as a victory since they have yet to be able to get a repeal bill all the way to the White House.

But the negotiations are complicated because the same complex rules that allow the legislation to be approved with a simple majority, instead of the 60-vote hurdle usually required, limit what can be included. Some of the elements included by the House bill face parliamentary obstacles in the Senate.

And Republicans have little margin for error. Commanding 54 votes, they can lose only three. And a provision aimed at cutting funding from Planned Parenthood is likely to cost at least one GOP senator, Susan Collins of Maine.

As a result it's unclear when, or even if, Republicans will be able to reach agreement and bring the bill to the floor, even as some question the wisdom of trying to broaden the bill's assault on Obama's health care program.

"Depends on what you want," said Sen. Jeff Flake, R-Ariz. "If you want to make a point, maybe. But not policy."