WASHINGTON — Donald Trump tried to assure skittish GOP lawmakers Thursday that they all share the same Republican Party goals, but Senate antagonists withheld support after a tense meeting with the presidential candidate.

Protesters chanted in sweltering heat outside, while inside a packed room at the Republican National Committee, Trump offered a simple message, according to Rep. Ken Calvert of California: “We all need to stick together. Things will all work out in November.”

With GOP lawmakers unanimous in their desire to beat Hillary Clinton this fall, some welcomed the reassurance and applauded Trump’s remarks.

It wasn’t enough for others.

Trump defended himself against some of his harshest Senate critics. Addressing Nebraska GOP Sen. Ben Sasse, he said, “Surely, you don’t want Clinton.”

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Sasse’s spokesman, in a statement, said the senator considers the two presidential choices as a “Dumpster fire,” adding that “nothing has changed.”

In one testy exchange, Trump recognized Sen. Jeff Flake of Arizona as a lawmaker critical of him. Flake referred to Trump’s criticism last year of his colleague, Sen. John McCain, who was captured and spent 5 1/2 years in a Vietnamese prison. Flake said he wanted to talk to Trump about those statements.

The exchange, first reported by The Washington Post, left Flake unwilling to back the nominee.

“My position remains, I want to support the nomination. I really do. I just can’t support him given the things that he’s said,” Flake told reporters later.

Sen. Mark Kirk of Illinois wasn’t in Thursday’s meeting, during which Trump supposedly called him a loser.

Asked if Trump could win his home state in November, Kirk said, “I don’t think so.”

Kirk said later, “We haven’t seen a personality like his too much in the Midwest. Eastern, privileged, wealthy bully. Our bullies are made of better stuff in Illinois.”

At a morning meeting with about 220 members of the House GOP, Trump discussed his policies and political organization, defended his remarks on Saddam Hussein Wednesday night and took questions.

Supporters of Trump, including both of Long Island’s Republicans, gave his appearance good reviews.

“There was a lot of good feeling in the room,” said Rep. Peter King (R-Seaford). “He showed today he could be Donald Trump and still work with Republicans. That’s what I got out of today’s meeting.”

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Rep. Lee Zeldin (R-Shirley) added, “I experienced nothing but positive vibes.”

But Rep. Charlie Dent (R-Pa.), who hasn’t endorsed Trump, said, “I said before the meeting that Donald Trump has a lot of work to persuade many Americans, including myself, that he is able to lead this great country. I still need to be persuaded.”

At the meeting, Trump brought up criticism of his praise of Saddam Hussein for killing terrorists and faulted the press for not reporting that he first said Saddam was a bad man, King said.

King said Trump also called him out in the meeting, in a friendly way, as they bantered back and forth. “He saw me and then he said, ‘I said one thing wrong and he said he didn’t agree with me on television,’ ” King said. “But he was smiling.”

With Tom Brune