Donald Trump's campaign launched a series of regular meetings with congressional supporters on Thursday in a bid to raise his stature in Washington and secure enough support to win the Republican presidential nomination.

Trump senior advisor Ed Brookover met near Capitol Hill with roughly a half dozen U.S. lawmakers who have endorsed Trump to detail how the Republican front-runner will win the 1,237 delegates he needs to secure the nomination ahead of the party's July 18-21 convention.

The informational meeting, which Trump did not attend, included lawmakers from states such as New York and Pennsylvania, which hold key nominating contests in coming weeks. It focused not on how to secure additional congressional endorsements but how to spread Trump's message on the ground among voters, attendees said.

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"This meeting was sort of a step one as we begin to transition from our primary (election) focus to becoming the nominee, toward the general election," Brookover told reporters.

Brookover added that Trump was on a "glide path" to the nomination and told lawmakers that conservative estimates showed the New York billionaire could win 1,265 delegates.

"We are going to start holding these (meetings) every week when we are in session," U.S. Representative Chris Collins of New York told reporters after the meeting.

New York holds its nominating contest on April 19. Trump holds a wide lead in opinion polls in his home state, where he has been campaigning intensely.

Trump's lightning-rod campaign is entering a new phase as the brash businessman seeks to improve relations with the Republican Party and generate more support for his anti-establishment presidential bid.

But progressive groups are continuing to hammer controversial statements Trump has made related to building a wall along the U.S.-Mexico border and a temporary ban on Muslims from entering the country.

MoveOn.org and other groups called for thousands of demonstrators who oppose Trump's positions to descend on a state party gala in New York City Thursday evening and at a fundraiser in the Long Island town of Patchogue, a suburb that is home to a large Latino population.

WAR OF WORDS

Trump himself has engaged in a war of words with the Republican National Committee and its chairman, Reince Priebus, over party rules that, for example, allowed party regulars in Colorado to choose a slate of delegates to send to the party's nominating convention without Republicans in the state actually voting.

All the Colorado delegates went to U.S. Senator Ted Cruz of Texas, who is trying to stop Trump from gaining the 1,237-delegate majority needed to win the nomination on the first ballot at the convention in Cleveland in July.

Failure to win the first ballot would open the way to a contested convention at which Cruz, Ohio Governor John Kasich or an 11th-hour dark horse could theoretically win a second or subsequent ballot and become the party's nominee.

Trump moved on Wednesday to strengthen his position in Washington by announcing he had hired Rick Wiley as his national political director. Wiley, a longtime Republican strategist, was the campaign manager for Scott Walker, the Wisconsin governor who dropped out of the presidential race last autumn.

Many members of the U.S. Congress have backed other Republican presidential candidates who have since abandoned the race.

"We'll be inviting other members" to subsequent meetings in the weeks to come so they spread Trump's message as they begin "campaigning in their individual districts, and all politics is local," Collins said.

U.S. House of Representatives Speaker Paul Ryan met with reporters as the Trump meeting was under way. Ryan said he had just returned from a trip to Israel, Egypt and Saudi Arabia that underscored his concerns about some of Trump's statements.

"Everybody pays attention to our politics," Ryan said, noting that he had denounced Trump's proposal to bar Muslims.

"People over there knew about it and thanked me for doing it," the speaker added.

Trump was set to address a fundraising event Thursday evening in Patchogue, the site of the fatal stabbing of Ecuadorean immigrant Marcelo Lucero in 2008 by a teenager who was part of a gang of white youths who targeted Latinos in the area.

The fundraiser's venue is near where Lucero was attacked, and immigrant advocates have planned protests there. Suffolk County Police Commissioner Timothy Sini said several different demonstrations coinciding with the event were expected.

After the fundraiser, Trump and Republican rivals Cruz and Ohio Governor John Kasich were to appear at the New York Republican Gala in Manhattan.

Progressive organizations have called on protesters to demonstrate at the event on social media sites such as Facebook. The gala is near Grand Central Terminal in Midtown, a busy railroad station, and demonstrations could snarl rush-hour traffic in the nation's most populous city.