David Jackson

USA TODAY

WASHINGTON — Donald Trump urged Republican lawmakers to get behind his presidential campaign Thursday, though tensions surfaced with critics who still refused to endorse their party's presumptive nominee — including one who described the election as a "dumpster fire."

Visiting Capitol Hill amid his search for a running mate and planning for this month's Republican convention, Trump blamed the media for campaign flaps that include his recent comments about ex-Iraq dictator Saddam Hussein.

He also complained about GOP lawmakers who have criticized him.

One GOP critic, Sen. Ben Sasse of Nebraska, spoke with Trump, but did not change his views.

"Mr. Sasse continues to believe that our country is in a bad place and, with these two candidates, this election remains a dumpster fire," said a statement from his office. "Nothing has changed."

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Another Republican critic, Sen. Jeff Flake of Arizona, mixed it up with Trump during the meeting.

Flake, who has said Trump's rhetoric and immigration proposals are alienating Hispanic voters, responded to Trump by referencing his past criticism of Sen. John McCain, a former Vietnam prisoner of war — Flake told the businessman that he is the senator from Arizona "who didn't get captured," the senator confirmed to reporters.

When Trump threatened to attack Flake publicly and predicted he would lose re-election, Flake responded that he is not on the ballot this year.

"I mentioned in there and I still hope to be able to support the nominee, but it's becoming increasingly difficult to think that that's possible," Flake later told The Arizona Republic.

Trump himself tweeted that he had "great meetings with Republicans in the House and Senate. Very interesting day! These are people who love our country!"

The New York real estate mogul also met privately with Texas Sen. Ted Cruz, a former primary rival, who told reporters he accepted an invitation to speak at the Republican convention that starts July 18 in Cleveland.

Many GOP lawmakers said they appreciated the chance to meet with Trump, while others said some skepticism of the candidate remains.

"We had a great meeting," House Speaker Paul Ryan, R-Wis., said after the session he described as an opportunity for House members "to get additional information about Mr. Trump’s campaign and ask questions."

Rep. Reid Ribble, R-Wis., a Republican who said he won't vote for Trump, said he did not think the New York businessman "moved the needle" with his appeal.

Republicans who “went in the room supporting him left just as enthused as they were when they went in," Ribble told the MilwaukeeJournal Sentinel. "People who are kind of negative on Trump, like me, left with the same feeling and maybe reinforced. And people on the fence are still on the fence.”

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Trump's separate meetings with House and Senate Republicans came amid GOP anxiety about sagging polls and continuing conflict about the outspoken businessman who is the party's presumptive presidential nominee.

Members who spoke with Trump said he complained about media coverage, citing the Hussein incident as an example. Trump said that, while he did argue that the former Iraqi dictator was good at killing terrorists, he also stressed he was a very bad person, officials said.

Sen. Bob Corker, R-Tenn., whom Trump considered for the running mate slot, said his colleagues developed a better understanding of Trump and his views. "It was most encouraging and helpful, and I think people felt — left there — feeling very, very positive," he said.

Democrats mocked Trump's meeting with Republicans on Capitol Hill, saying the GOP is linking itself to the candidate's extreme views on issues like immigration.

Republicans "acknowledged Trump as their political and philosophical leader" by welcoming him to the Hill today," said House Minority Leader Nancy Pelosi, D-Calif. "There's not a dime's worth of difference between Donald Trump and House Republicans."

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As he evaluates potential running mates and makes final preparations for the GOP convention, Trump says he wants Republican unity heading into the fall election — but doesn't think it is essential.

"Now, you know, we need unity in the Republican Party," Trump said this week in Raleigh, N.C. "I have to be honest — I think I'll win without the unity. But we need unity in the Republican Party."

Not every Republican showed up to the Trump meetings Thursday.

McCain and Sen. Kelly Ayotte of New Hampshire, both of whom face tough re-election bids in November, said they had to attend a Senate Armed Services Committee meeting. Sen. Marco Rubio, R-Fla., one of the presidential candidates defeated by Trump in the Republican primaries, presided over the Senate at the time of the Trump meeting.

Many Republican lawmakers also do not plan to attend the GOP convention.

Elections 2016 | USA TODAY Network

The presumptive Republican presidential nominee spoke with lawmakers as he narrows his search for a vice president.

Among the possibilities: Indiana Gov. Mike Pence, former House speaker Newt Gingrich, New Jersey Gov. Chris Christie, Alabama Sen. Jeff Sessions and Arkansas Sen. Tom Cotton.

Other potential nominees — including Corker and Sen. Joni Ernst of Iowa — have bowed out of the process.

Contributing: Craig Gilbert, Donovan Slack and Erin Kelly