WASHINGTON — Six months after assuming control of both chambers of Congress and the White House, Republicans are struggling to pass major parts of their ambitious legislative agenda, and they face a growing list of controversial issues that are testing the party’s ability to govern.

In Congress, Republicans have been unable to bridge differences between diverse factions of the party on health care reform, a dynamic that threatens to intrude on other major issues like the federal budget. At the White House, President Donald Trump has been mired in investigations that have consumed much of his time, leaving him an ineffective chief spokesperson for the party and their ideas.

Unity on major issues has proven elusive for a party with a wide swath of ideologies, ranging from northeast centrists to religious conservatives, fiscal conservatives and small-government libertarians — a complicated mixture that hampers leaders from assembling a reliable coalition of votes.

That dynamic has stymied the GOP on health care, an issue that appeared simple for the past seven years on the campaign trial and when Trump promised it would be done “on day one.” The GOP Congress easily passed a bill to repeal Obamacare in 2015, when they knew there was no chance that President Barack Obama would sign it into law.

Now that their actions would become reality, finding any solution that a majority of the party can take home to their voters has fallen short, at least so far.

And the same divisions that are making health care difficult are also threatening the rest of the GOP's legislative agenda.

Republicans in the House of Representatives are trying to pass a budget resolution but that is being stalled because they are having trouble finding enough Republican votes to pass it. The conservatives in the House Freedom Caucus are pushing for $400 billion worth of cuts while the moderates want to keep the current budget levels. Republican leadership has proposed a compromise: $200 billion in cuts. But as of now, neither side is budging and the budget probably won’t be passed before the House leaves for its scheduled five-week recess next week.

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Related: Confusion Grips Senate GOP Ahead of Expected Health Care Vote

A fight over the budget will impact one of the GOP's highest priorities, tax reform, not only politically but substantively. The amount of money cut from the budget resolution determines how much less Republicans will have to work with on tax reform.

“It’s a problem we’ve had as a party for some time,” said Rep. Charlie Dent, R-Penn., and chair of the moderate Tuesday Group in the House, of his party. “We saw this going back to the shutdown. One year it was defunding Obamacare, the other it was Planned Parenthood, now it will be the border wall. Somebody will find a reason to say we can’t fund the government unless we get ‘x’. Someone always finds an issue.”

The party is also girding for a fight on the upcoming debt ceiling that must be lifted by the end of the fiscal year, which is an issue that has for years divided the party.

The Republicans’ legislative problems are made more complicated by an unpredictable president in the White House. Republicans publicly are giving Trump a pass on not doing enough to help them advance their agenda. But privately, Capitol Hill aides are frustrated and feel abandoned by a president consumed with ongoing investigations into Russia and his seemingly single-minded focus on it. In addition, aides admit that Trump has not shown a commitment to learning details necessary to successfully sell legislation to both skeptical members and the public.

Rep. Tom Cole, R-Okla., defends the House of Representatives, which did eventually pass a health care bill, but he admits that turmoil at the White House is dominant.

“Honestly, I think there have been so many distractions that most people don’t know how much we have done,” Cole said.

Trump, a different breed of Republican who has repeatedly shown little loyalty to the party, has also actively worked against members of his own party at times. A super PAC supporting Trump launched television ads against Sen. Dean Heller, R-Nev., after he came out against the first health care bill. The super PAC took down the ads after Republican leaders quietly protested and Heller brought it up directly with the president during a health care gathering.

Trump later joked in front of Heller and his colleagues and the press, “He wants to remain a senator, right?”

Heller hasn’t been Trump’s only target. The White House has met with primary opponents to Sen. Jeff Flake, R-Ariz., who is up for re-election in 2018. Kelli Ward, Flake’s primary opponent, told NBC News she was “more encouraged” to run after a recent meeting at the White House.

While Flake refused to comment about the White House working against his re-election, his colleagues said it’s not helpful.

“I want to see all our senators come back, so I would prefer that they would focus on defeating the Democratic opponents and invest their time and resources and energy on that,” said Sen. John Thune, R-S.D., and Republican conference chairman.

Senate Majority Leader Mitch McConnell has said there will be a Senate vote on health care early this coming week. Whatever the outcome, GOP leaders are anxious to move forward to other agenda items but their intra-party differences could prove a bigger challenge than the shrinking calendar.