WASHINGTON — Congressional Republicans struggled to tamp down a family feud Thursday as they approached a politically charged showdown with the White House that combines the threat of a government shutdown, a possible first-ever federal default and the GOP’s bid to repeal the nation’s three-year-old health care law.

One day after conceding that the Democratic-controlled Senate probably would prevail on the last part, Sen. Ted Cruz still vowed to do “everything and anything possible to defund Obamacare.” That includes a possible filibuster of legislation to prevent a partial government shutdown, added the Texas Republican.

That was a step further than Sen. Mike Lee of Utah — Cruz’s partner in a summertime run of “Defund Obamacare” television commercials — was willing to go. President Barack Obama’s health care law “is not worth causing a shutdown over,” he said.

The two men spoke at a news conference with several House Republicans where lawmakers stressed they were unified and thanked Speaker John Boehner for agreeing to tie the anti-shutdown and anti-Obamacare provisions into one bill.

That bill is on track for House passage on Friday, with a Senate showdown to follow.

The House intends to move quickly next week with a separate bill to put the health care law on ice, this one a measure that also would allow the Treasury to avoid a default that could destabilize the economy.

Boehner himself sought to redirect the political fire at Obama, accusing him of being ready to negotiate with Russian President Vladimir Putin over Syria but not engage with Republicans on raising the nation’s debt limit, an issue that could lead to national default.

But he also got in a subtle jab at Cruz and Senate conservatives who have been clamoring for weeks for a showdown on the health care law.

“I expect my Senate colleagues to be up for the battle,” he said.

The prospect is for a 10-day period of intense uncertainty, with Boehner pledging to avoid a shutdown yet also hoping to come away with a bite out of the health care law, even if less than complete defunding.

Congressional aides pointed out during the day, for example, that if the Senate rewrites the House-passed bill to leave the health care law in place, Boehner and the rest of the House leadership could still seek further changes before passing it a second time.

For their part, the White House and majority Democrats in the Senate will be trying to protect the health care law that stands as Obama’s signature domestic accomplishment — without complicating the re-election chances of senators on the 2014 ballot in swing states.

The White House intruded briefly on the Republican feud, pledging that Obama would veto any legislation that blocks the health care law from taking full effect. The defunding drive “advances a narrow ideological agenda that threatens our economy and the interests of the middle class” and would deny “millions of hard-working, middle-class families the security of affordable health coverage,” it said.

The effort seeking virtual repeal of the law as part of a government funding bill gained powerful momentum over the summer when the Senate Conservatives Fund, Heritage Action and other groups with tea party ties launched a nationwide campaign.

Cruz and Lee played prominent roles, each appearing in television ads aimed at pressuring Republican lawmakers not to yield. “Republicans in Congress can stop Obamacare if they simply refuse to fund it,” Lee says in one SCF-funded commercial.

On the other hand, the U.S. Chamber of Commerce has urged Republicans to fund the government and prevent a default, then double back and try and work out changes to the health care law later.

In a tea party age, it is unclear how much political clout establishment groups carry with individual GOP lawmakers.

At the same time, many Republicans fear a replay of twin government shutdowns nearly two decades ago that inflicted significant damage on their party and helped resurrect then-President Bill Clinton’s political fortunes.

“I’m one who doesn’t believe that a shutdown does anything except divert attention from a president and his policies, which are rightfully unpopular, to congressional incompetence,” said Sen. John Cornyn, R-Texas. “We’ve seen what happens when Republicans are divided, we basically cede power and influence on the outcome.”

Cruz saw it differently hours earlier.

He told The Associated Press that the 1995-96 episode was just a “partial, temporary government shutdown” that didn’t hurt Republicans politically as much as most people think and that it helped bring welfare reform in 1996 and a budget deal in 1997.

“Nobody likes that outcome. But it also wasn’t the end of the world,” he said of a possible shutdown.

Ironically, it was a Cruz comment that ignited anger among House conservatives on Wednesday evening.

As word spread that the House would pass legislation to fund the government and cut off money for the health care law, he issued a statement that said Senate Majority Leader Harry Reid “likely has the votes” to delete the health care provision. “At that point, House Republicans must stand firm, hold their ground, and continue to listen to the American people,” he said.

House Republican aides said rank-and-file lawmakers on the House floor at the time vented their anger at what appeared to be a pre-emptive surrender.

Rep. Sean Duffy, R-Wis., tweeted that Lee and Cruz “refuse to fight. Wave white flag and surrender.”

Rep. Lynn Westmoreland, R-Ga., tweeted, “Senate R’s already declare defeat… before the battle even begins. So much for standing up for the American people.”