Donald Trump Finds Praise on Capitol Hill, but No GOP Endorsements

— -- Lawmakers welcomed Donald Trump to Washington Wednesday to rally against the Iran nuclear agreement, praising the success of his campaign but stopping short of offering any endorsements.

Taking the stage outside the Capitol to R.E.M.’s “The End of the World,” the Republican front-runner criticized the Obama administration’s negotiations on the Iran deal.

“Never, ever, ever in my life have I seen any transaction so incompetently negotiated as our deal with Iran,” Trump proclaimed, saying Americans “may get bored with winning” under his administration.

Rep. Steve King, R-Iowa, who supports Trump’s hard line on immigration, said the New York real estate mogul’s appeal comes from his confidence.

“We’ve had presidents that didn’t make us proud to be Americans,” he said. “Trump is still working on the art of humility, but he’s put the swagger back in Americans.”

King is undecided on whom he will back, but expects members to endorse Trump as the race continues.

“I can’t imagine that not happening when you’re running first in the polls,” he said.

Freshman Rep. Lee Zeldin, R-N.Y., who has been a prominent opponent of the Iran deal as Congress’s only Jewish Republican, broadly praised Trump’s positioning on foreign policy.

“He understands that our enemies do not respect weakness,” Zeldin said.

While Zeldin also said he wasn’t prepared to endorse Trump or any other candidate, he also complemented Trump’s persona.

“Americans want candid, brutally honest, sometimes politically incorrect leadership,” he said.

Rep. Trent Franks, R-Ariz., suggested Trump’s past positions and history as a Democrat may prevent some Republican politicians from endorsing his campaign.

“Donald Trump has not always been pro-life, and I hope that his conversion is complete,” said Franks, who is supporting former Arkansas Gov. Mike Huckabee.

Former Minnesota Gov. Jessie Ventura and former Republican vice presidential candidate Sarah Palin have both spoken favorably of Trump's presidential campaign, and Palin has said she'd serve as Trump’s energy secretary.

While he didn't leave Washington with any new backers, Trump did get a meeting with Alabama’s Sen. Jeff Sessions, a Republican who has advised his campaign on immigration policy.

“Mr. Trump has outlined trade and immigration policies that serve the national interest, not the special interests,” Sessions said in a statement. “Anyone who wants to sit in the Oval Office must promote trade and immigration plan that improve jobs and wages for Americans.”

ABC News’ Ali Weinberg contributed to this report.