WASHINGTON — What’s old is new again for Sen. Ted Cruz — fighting for a full repeal of the Affordable Care Act.

But once again, the opponent is his own party.

Since losing the party’s nomination to Trump last year, Cruz has tried to make nice with GOP colleagues in Congress. But as a sharply divided Republican caucus wrangles over how and when to repeal and replace the health care law, Cruz is returning to his most comfortable role: the Hill’s agitator-in-chief.

This week, Cruz and fellow Republican Sens. Mike Lee and Rand Paul blasted a leaked draft replacement proposal crafted by Speaker Paul Ryan and other House GOP leaders, including Texas Rep. Kevin Brady, arguing it doesn’t go far enough to repeal the law.

Staunch conservatives in the House, along with outside organizations, quickly jumped in, calling the Ryan draft “Obamacare-Lite.”

When you spend 6 years promising, “If only we get elected, we’ll repeal Obamacare,” you can't renege.#FullRepeal https://t.co/IeWvSyo3fg pic.twitter.com/GrkD886bbo — Ted Cruz (@tedcruz) March 3, 2017

They argue that Congress should turn to language in a 2015 repeal bill as the "bare minimum" for the GOP's draft legislation. Cruz has said lawmakers should fully undo the law now, even if they haven't reached consensus on a replacement, and even if it means Vice President Mike Pence must overrule Senate parliamentary procedures governing the process.

But Republican leaders — many concerned about the toll that repealing without replacing would have on the health insurance market — are eyeing what many have termed a “piecemeal” approach.

They have also vowed to repeal the Affordable Care Act, but aim to undo the thorny health care law through a series of repeal measures and potentially administrative actions from the White House.

House leaders, including Brady, have said the leaked draft is outdated. But few observers expect the key components of the measure to dramatically change when it’s introduced in coming weeks, which could pit Cruz and conservative members against Republican leadership.

The disagreement has the makings of Cruz's first major congressional battle since Donald Trump became president.

“We should focus on areas of consensus that bring Republicans together,” Cruz told Fox News this week. “I'm working very, very hard to try to bring my colleagues together in both the Senate and House with the administration to fulfill the promise to the American people.”

But asked by The Dallas Morning News how far he's willing to go in his latest battle, the senator who led the 2013 government shutdown over Obamacare — and is hardly considered a consensus builder — simply said: "Failure is not an option."

Cruz’s position could make life difficult for Republicans — and potentially Trump — as they are under the gun to make good on their collective campaign promise to undo the health care law.

Unlike fellow Texan John Cornyn, Cruz doesn’t sit on any of the committees with primary jurisdiction over the health care law overhaul. But his support will be crucial in the end, as there’s little margin for error in the Republicans’ four-seat majority in the Senate.

“It’s critical. I don’t think we can get what we need to get done without almost universal support,” Cornyn said, noting Republicans have 52 senators and need 51 to pass the bill that will serve as the primary vehicle for dismantling the ACA. “There’s not a lot of room for freelancing.”

But Cornyn, who as the No. 2 Republican in the Senate will need to secure all necessary votes, shrugged off Cruz’s stance as “constructive.”

“The hard part for Republicans is that Republicans are entrepreneurial and everyone has an idea and a better way,” he said. “But the fact is we can only pass one bill, and that’s why it’s so important that we be aligned with the House and the White House.”

If Republicans hoped Trump would take a side on the issue during his joint address to Congress this week, some may have been disappointed.

President Donald Trump spoke only of general principles for replacing Obamacare during his address to Congress this week. (Jim Lo Scalzo/The Associated Press)

Trump endorsed a full repeal but spoke of only general principles for a replacement. He voiced support for the use of expanded health savings accounts and tax credits — an idea Cruz and other conservatives have previously denounced as an entitlement, but others defend as a way to expand health care access to those without employer-sponsored or government-provided insurance.

But the president didn’t wade into whether Republicans should repeal the law in one fell swoop or through a series of measures.

House Majority Whip Steve Scalise said he heard an endorsement for Ryan’s plan in Trump's words this week.

Cruz didn’t.

“I don’t doubt that an awful lot of people see an endorsement in things the president says,” he told reporters, adding: “The president was laying out principles.”

Asked if he’d drop his opposition if Trump ultimately backs the leaders’ plans, Cruz reserved comment until the legislation becomes public. But “of course, the president’s support is going to carry weight in Congress,” Cruz said.

Cruz hasn't gone as far as Paul, the Kentucky conservative, in making a fuss. This week, Paul blasted House leaders for keeping the GOP bill under lock and key, even leading reporters to a committee room where he demanded, unsuccessfully, to see a copy of the draft.

Sen. Rand Paul, R-Ky., blasted House Republican leaders, saying they're keeping their Obamacare repeal-and-replace legislation under lock and key. (J. Scott Applewhite/The Associated Press)

Adam Brandon, the chief executive of the conservative activist group FreedomWorks, is among those counting on Cruz, Lee and Paul to deliver results.

The organization is advocating for a full repeal now and has opposed parts of Ryan’s health care agenda.

“Whatever we do to Obamacare, this is the one last shot to put in patient-centered health care. This is worthy of political turmoil. This is worthy of losing a Senate seat,” Brandon said, adding that the men “have a lot of political capital, and they have to spend some of it right now.”

But Reed Galen, a Republican strategist who worked with Cruz on former President George W. Bush’s 2000 campaign, predicted the senator will be more focused on self-interested politics than policy.

“He will take a position that is most politically advantageous to him, knowing that nothing will likely come of it. If he gets what he wants, big win,” Galen said. “If he doesn’t, he can rage against the D.C. machine back home — where’s he got little-to-no legislative record to speak of for his re-election campaign.”

Democrats, who have said they’re willing to work with Republicans to fix the law only if they drop their repeal efforts, watch with some bemusement as Cruz and GOP leaders prepare to tussle.

Some note Cruz’s brewing opposition could work in their favor if Republicans remain divided.

“It does help us to have some folks stake out really extreme positions,” said Sen. Chris Coons, D-Del. “As long as we’re [ultimately] able to negotiate something that moves the country forward and helps provide access to quality health care.”