Republican senators are coming to the aid of Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE following President Trump's recent string of attacks against the Kentucky Republican.

Five GOP senators offered their support for McConnell on Thursday after the president escalated his war of words with the Senate leader, arguing he's failing to pass the GOP's legislative agenda.

Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R-Nev.) backed McConnell on Twitter, saying he would help lead the conference during its coming push this fall on tax reform — a key GOP agenda item along with healthcare.

"I look forward to [McConnell's] leadership as we work to reduce Americans’ taxes," Heller — the most vulnerable GOP senator up for reelection next year — said.

Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (R-Ariz.), a vocal critic of Trump, added that McConnell "does a tough job well. He has my support. "

.@SenateMajLdr does a tough job well. He has my support. — Jeff Flake (@JeffFlake) August 10, 2017

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Those two are considered the most vulnerable Senate Republicans up for reelection in 2018. They've also been targeted directly by Trump or his allies in the past.

"[McConnell] will continue to lead our caucus [and] bring us closer together to keep the promises we made to the American people," he said in a series of tweets . "All GOP officials must work together so we can advance our shared agenda."

Sen. Chuck Grassley Charles (Chuck) Ernest GrassleySenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE (R-Iowa) told a local radio station that he had "a lot of tolerance" for McConnell "because he kept the caucus together" when Republicans blocked Merrick Garland, former President Obama's Supreme Court nominee, from getting a hearing or a vote in 2016.

"You can be a majority leader, but each senator controls their own vote," Grassley, the chairman of the Judiciary Committee, said, according to The New York Times.

Sen. Orrin Hatch Orrin Grant HatchBottom line Bottom line Senate GOP divided over whether they'd fill Supreme Court vacancy MORE (R-Utah), the chairman of the Senate Finance Committee and a key senator of the upcoming tax reform fight, became the first GOP senator to publicly back McConnell amid Trump's escalating attacks.

"[McConnell] has been the best leader we’ve had in my time in the Senate, through very tough challenges. I fully support him," Hatch, the most senior Republican senator, wrote in a tweet.

Kevin Smith, a spokesman for Sen. Rob Portman Robert (Rob) Jones PortmanRomney undecided on authorizing subpoenas for GOP Obama-era probes Congress needs to prioritize government digital service delivery House passes B bill to boost Postal Service MORE, said the Ohio Republican also supports McConnell as leader.

"If we’re going to accomplish our goals on tax reform, healthcare, the opioid crisis and other issues, we have to work together," Smith told Business Insider.

Trump has launched a verbal firestorm against McConnell after the Kentucky Republican said the president's "excessive expectations" were partly to blame for the narrative that Republicans haven't been able to accomplish anything.

The president appeared to threaten McConnell earlier Thursday, leavening the door open to him considering stepping down as the Senate majority leader if he can't pass the GOP legislative agenda including healthcare, tax reform and infrastructure.

“If he doesn’t get repeal and replace done, and if he doesn’t get taxes done — meaning cuts and reform, and if he doesn’t get a very easy one to get done — infrastructure — if he doesn’t get them done, then you can ask me that question,” Trump told reporters at his New Jersey golf club when asked whether McConnell should step down.

The comments came after three tweets during the past two days targeted McConnell for his comments at a Rotary Club in Kentucky.

"Our new president has, of course, not been in this line of work before, and I think had excessive expectations about how quickly things happen in the democratic process,” McConnell said earlier this week.

He added there were “artificial deadlines” on how long it took to pass bills that were “unrelated to the reality of the complexity of legislating.”

The verbal volleying comes after Republicans failed to make good on their years-long pledge to repeal and replace ObamaCare. A "skinny" repeal proposal failed in a dramatic vote. A broader repeal measure, as well as a plan to repeal and replace ObamaCare simultaneously, also failed to get enough votes to pass.

Despite the blow to a key GOP agenda item, McConnell has strong support among Senate Republicans, who reelected him to the top spot unanimously late last year.

While several GOP senators publicly voiced frustrations about the closed-door process on healthcare, they stopped well short of questioning McConnell's status as majority leader.

But not every GOP senator has been willing to step into the middle of McConnell and Trump's battle.

Sen. Lindsey Graham Lindsey Olin GrahamMomentum growing among Republicans for Supreme Court vote before Election Day Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Warning signs flash for Lindsey Graham in South Carolina MORE (R-S.C.) told Fox News on Wednesday that his party "promised for eight years to repeal and replace ObamaCare."

“I like Mitch, but for eight years we’ve been saying we’re going to repeal and replace ObamaCare; it’s not like we made this up over night,” Graham, who laughed after listening to McConnell’s comments, told Fox News’s Brian Kilmeade on Wednesday.

Asked again about the back-and-forth on Thursday by conservative radio host Hugh Hewitt, he appeared to take a more muted stance, simply saying that both Trump and McConnell should focus on healthcare.

Sen. Ron Johnson Ronald (Ron) Harold JohnsonThe Hill's Morning Report - Sponsored by The Air Line Pilots Association - White House moves closer to Pelosi on virus relief bill Second GOP senator to quarantine after exposure to coronavirus GOP-led panel to hear from former official who said Burisma was not a factor in US policy MORE (R-Wis.), asked about Trump's comments by CNN's "New Day," said, "I'll let this president speak for himself and his tactics."

"But, you know, the fact of the matter is, is we need to come up with the policies that reduce gross premiums. ... And we need to be courageous and we need to be honest in terms of what the root cause analysis is. And that's in the lap of Congress, quite honestly," he said.