Congressional Republicans are bracing for another round of name-calling and criticism from President Trump before returning to Washington next month, fearing his outbursts will complicate their legislative agenda as such behavior becomes a defining feature of his presidency.

Trump took aim at three GOP senators in a torrent of bitter tweets last week. Those tweets left much of Capitol Hill wondering if the Republican president is so preoccupied with protecting his current image that he has forgotten his broader legacy will be defined by what he accomplishes at the end of four or eight years.

"Some Republicans feel Trump is only concerned with building his brand and not the brand of the Republican party," Republican strategist Noelle Nikpour told the Washington Examiner on Thursday, hours after Trump slammed Senate Majority Leader Mitch McConnell, R-Ky., for failing to shepherd an Obamacare replacement bill through the upper chamber last month. The next day, Trump warned Tennessee Sen. Bob Corker his home state "is not happy!"

"All the GOP members he continues to trash in public he will eventually need to pass his legislation in the future," Nikpour said.

Arizona Sen. Jeff Flake, the third Republican lawmaker to be publicly criticized by Trump this week, said the president is "inviting" a 2020 challenge from someone in his own party with his current style of governing and his vitriol on social media.

"The direction he's headed [in] right now, just kind of drilling down on the base rather than trying to expand the base – I think he's inviting one," Flake told a Georgia radio station Wednesday.

White House officials privately admitted Trump's assault on members of his own party has made it more difficult for them to work with congressional offices and coordinate on legislation.

One official told the Examiner they spent more time answering questions about the president's messaging strategy "than his strategy for tax reform" during a recent meeting with a Senate GOP aide.

Publicly, the White House has blamed Congress for inaction on items like tax reform. White House officials say the president's keyboard is a tool he can use to pressure lawmakers to buckle down so Republicans can finally claim a major legislative win.

"It's clear that the end game is for Congress to do its job and actually pass legislation," White House press secretary Sarah Sanders said Friday. "I think the American people are very frustrated with Congress' lack of action … and we're looking for them to step up at this point."

Republican lawmakers will face a long to-do list when they return in September, as they must decide to raise or suspend the debt ceiling at the risk of facing steep economic and political consequences. Separately, lawmakers must pass an omnibus spending package containing all 12 appropriations bills or approve a continuing resolution that sustains government operations until a later date.

"Our goal is to get the debt ceiling and some sort of funding bill done before those deadlines and then move on to committee work on tax reform," said a senior GOP aide.

But the aide cautioned that much of what Congress is able to accomplish will depend on how active and disciplined Trump is when it comes to the GOP's tax reform push, and whether he can avoid further damaging his relationship with McConnell and other Senate Republicans.

"We might have a bunch of other tweets before [Congress] returns, and I'm sure it's something a lot of senators are going to be asked about when they do get back," the aide said, adding the president's affinity for the popular social media platform has made Republicans' lives "a little more difficult and forced us to talk about things that we don't necessarily want to talk about."

The aide continued, "I heard someone say recently that you kind of just have to move forward and not expect much help from the White House, and I guess that's mostly true. If they can go out and really sell tax reform, that's great. But I'm not really holding my breath on that."

Beyond his criticism of GOP senators, Trump's recent threat to shutter government agencies over funding for his promised border wall has further complicated matters for members of his party on Capitol Hill.

Vetoing legislation that excludes money for the border wall would prove Trump remains committed to his most contentious campaign promise. It would also exacerbate the growing rift between himself and congressional Republicans.

"I don't think a government shutdown is necessary, and I don't think most people want to see a government shutdown, ourselves included," House Speaker Paul Ryan said last week during an appearance in Oregon.

Any move that further isolates the president from his own party will not just make September a difficult month, some believe it will make Republicans less competitive in the 2018 midterms.

"One thing the Democrats have is unity. They may have policies that are not good for the economy but they all follow the leader and vote for them," Nikpour told the Examiner. "As a national fund raiser, what am I to sell to my donors? I used to sell that if we had a GOP House, Senate, and President we could pass everything we need to be successful."

"[That] is not happening," she said.