WASHINGTON — After a year of legislative fits and starts, the Republican-led Congress can claim victory on an agenda of tax cuts, judicial confirmations and a substantial regulatory rollback.

It’s a list of accomplishments that seemed to surprise even party leaders, who warily entered a political marriage of necessity with President Donald Trump, but now say they have made their peace with his unpredictable style of governing.

“I’m warming up to the tweets, actually,” Senate Majority Leader Mitch McConnell, R-Ky., said Friday after the president showered Congress with Twitter praise. “This has been a year of extraordinary accomplishment, by any objective standard.”

The successes, however, have come at a steep political price. Polls show voters unenthusiastic about the tax overhaul — the GOP’s signature accomplishment — and preferring Democrats over Republicans in Congress by historically wide margins. Republican strategists concede that their majority in the House — and perhaps in the Senate, as well — is at serious risk in next year’s midterm election.

The path for the party doesn’t seem likely to get any easier in the coming year. Pushing the tax-cut bill to Trump’s desk — he signed it into law Friday — was a lighter legislative lift than any of the options for what comes next.

Lowering tax rates has been a longtime top GOP priority and one most Republican lawmakers agree on. By contrast, party leaders already disagree about the agenda for next year.

House Speaker Paul Ryan, R-Wis., has announced that he wants to overhaul welfare and so-called entitlements in 2018, utilizing the same strictly partisan rules Republicans relied on to approve their tax measure without Democratic votes or a filibuster threat in the Senate.

“One of the important entitlement reforms we see that is necessary is get us out of this poverty trap,” Ryan told reporters. “We have tens of millions of people right here in this country falling short of their potential, not working, not looking for a job, or not in school getting a skill to get a job. That’s a problem.”

But McConnell does not want Republicans to take on such a divisive issue in an election year, when GOP senators could be blamed for unpopular cuts in safety net programs at a time when many Americans continue to struggle in a shifting economy.

“Here’s my only observation about entitlement reform,” McConnell said. “The sensitivity of entitlements is such that you almost have to have a bipartisan agreement in order to achieve a result.”

Similarly, Ryan and other Republicans have talked about trying again to repeal the Affordable Care Act. McConnell shrugged off the idea Friday, saying, “Well, I wish them well.”

McConnell, who struggled this year with a two-vote margin of control in the Senate, faces an even tougher task in the new year, when Democrats add to their ranks with the arrival of Doug Jones, the senator-elect from Alabama, who will make the Senate balance 51-49.

Congress left behind a lengthy to-do list of unfinished work when lawmakers quit for the year, approving only a stop-gap agreement to fund the government and setting up another budget showdown on Jan. 19. They failed to resolve issues that include disaster relief, reforming the National Security Agency’s surveillance programs and whether to protect young immigrants from deportation who were brought to the U.S. illegally as children and are sometimes referred to as Dreamers.

The White House has not made matters easier, failing to lay out a clear strategy for next year.

Trump and GOP leaders plan to meet at the White House in January to draft a shared agenda. One strong possibility is some form of an infrastructure measure, although Trump has talked about that for a year without proposing a specific plan.

Serious new spending on roads, bridges and airports, as Trump has sometimes suggested, would run into objections from Republican conservatives. But a package that relies on tax breaks for developers or complex financing schemes would open the GOP to attack by Democrats.

An immigration package that would resolve the status of the Dreamers in exchange for tougher border security enforcement is also likely to be on the list.

Trump campaigned on working across the aisle to change Washington’s gridlock, but, so far, the White House has been unable to woo many Democratic votes to his side.

“At some point, and for the good of the country, I predict we will start working with the Democrats in a Bipartisan fashion,” Trump tweeted Friday. “Infrastructure would be a perfect place to start. After having foolishly spent $7 trillion in the Middle East, it is time to start rebuilding our country!”

Trump often repeats the $7 trillion claim, although the White House has not cited a basis for it, and outside experts say it is a considerable overestimate for the cost of the wars and rebuilding in the region.

Democrats, emboldened by constituents who are deeply resistant to Trump, have found little incentive to work with the president.

Their voters want representatives in Washington to challenge the White House, not enable it, as seen by robust Democratic turnout in off-year elections, including Jones’ victory in Trump-country Alabama.

Democrats are almost certain to resist any Republican proposals for deep spending cuts, especially after GOP passage of the $1.5 trillion tax cut.

“They’re in for the fight of their lives if they’re going after Medicare, Medicaid and Social Security,” said Sen. Dick Durbin of Illinois, the Senate’s No. 2 Democrat.

“It is just perfect isn’t it? Tax breaks for the wealthiest people who haven’t punched a time-clock in their lives so that we can cut back food stamps for single moms trying to feed hungry kids,” Durbin said.

lisa.mascaro@latimes.com