Trump met with a number of his backers in Congress at a law office on Capitol Hill, including Alabama Sen.
And ahead of a speech to a leading advocacy group for Israel, he named several foreign policy advisors for the first time, including a former Army officer and a consultant on international oil and gas businesses. The list also included his son-in-law, Jared Kushner, a real estate investor who Trump says helped him draft his address after speaking to "many of his friends in Israel."
But as is usually the case with Trump, the day included several unorthodox moments. He opened a news conference with a five-minute pitch for his luxury hotel conversion in Washington. He questioned the existence of NATO. And he ended his speech by saying he would love for his pregnant daughter to give birth right then.
Still, Trump tried to underscore what he viewed as his growing appeal. He said his support in the Republican establishment is broader than what it appears: "Some people go on television saying, 'We have to stop Donald Trump,'" but privately are asking him for meetings, he said, declining to identify who he's talked to in the anti-Trump faction that has coalesced in recent weeks. Trump said his remaining foes in the Republican establishment should get on board and quit trying to block his path to the nomination.
If conservative opponents run a third-party candidate, he said, it would virtually guarantee a Democratic victory. "You can't be that spiteful," Trump said in a news conference at Washington's Old Post Office, which he is converting to a luxury hotel a few blocks from the White House. "Otherwise you'll destroy the country."
Leading Republicans like House Speaker Paul D. Ryan, who has criticized Trump, were not at the Capitol Hill meeting, but the spokesman for one Trump supporter said the "constructive" meeting was a sign that the party is coming around to Trump.
"It's obvious that Trump's support is broadening," said Joe Kasper, a spokesman for Rep.
In his remarks Monday, Trump again said he favored trying to steer away from military actions abroad, saying that the U.S. had to focus on rebuilding its economy and military first. "We're sitting on a big, fat financial bubble," he said.
In a speech to the convention of the American Israel Public Affairs Committee, a leading pro-Israel lobbying organization that is a customary stop for presidential hopefuls, Trump gave an uncharacteristically staid speech with themes tailored to the pro-Israel crowd.
In a departure from his shambolic, off-the-cuff approach in his campaign rallies, Trump mostly stuck to prepared remarks read from a teleprompter. Criticized for vague proposals, he peppered his address with details on ballistic weapons and terrorist groups.
Trump, who had said during a Republican debate that he would want to appear "somewhat neutral" in order to negotiate a peace deal between Israelis and Palestinians, sided decisively with Israel in his remarks Monday night.
Earlier in the day, Hillary Clinton criticized what she viewed as Trump's varying positions on Israel in her own speech to the group. She didn't name Trump but her reference was clear.
"We need steady hands, not a president who says he's neutral on Monday, pro-Israel on Tuesday and who-knows-what on Wednesday because everything's negotiable," she said.
In another sign of Trump and establishment Republicans taking tentative steps toward one another, Trump said he would enlist the Heritage Foundation to help him compile a list of potential Supreme Court nominees, a way to court conservatives concerned about who will fill a vacant seat on the court.
In a meeting at the Washington Post, Trump said his foreign policy advisors included Carter Page, an international energy consultant, and Gen. Joseph Keith Kellogg, who served as an officer in Iraq after the U.S.-led invasion. Trump has criticized the decision to invade Iraq. Trump said they didn't have to agree. "It doesn't mean I'll use what he's saying, but I like different opinions," he said.
Asked about the violence at his rallies, Trump briefly said, "I don't want violence," before launching a lengthy defense of his supporters, including the man who was filmed punching and kicking a protester at a rally in Tucson on Saturday.
"These are not good people," he said of protesters. "The people who are supporters are unbelievably good people."
Trump also couldn't resist some salesmanship. He spoke at his news conference in front of two American flags, behind a lectern with a sign that said Trump Hotels, not Trump for president. He later led a jostling scrum of reporters on a short tour of the building, fielding questions as he walked past piles of drywall and insulation.
"As people who love this country, I think you'll be very proud of it," he said of the project.