More rank-and-file Republicans are expected to follow suit, including longtime Republican lawmaker John Duncan
Republican presidential front- runner Donald Trump has netted three major endorsements, including from two House committee chairmen, signalling that the party leadership is warming to the real estate tycoon.
"An aura of inevitability is now forming around the controversial mogul," The Washington Post said after Trump, 69, was endorsed by two House Republican committee chairmen, Bill Shuster and Jeff Miller.
Indiana University basketball coach Bob Knight also threw his support behind Trump's presidential campaign, less than a week before Indiana voters go to the polls in the state's primary.
News reports said more rank-and-file Republicans are expected to follow suit, including longtime Republican lawmaker John Duncan.
"Establishment Republicans are warming to the idea of Donald Trump as the GOP standard-bearer," The Hill reported.
"The realisation is that Donald Trump is going to be our nominee. We're coming to the end of the process; its time to unite the party and take on Hillary," Trump supporter Tom Reed was quoted as saying by The Hill.
After this Tuesday's primary elections, Trump is now way ahead of his other rivals in terms of delegate count and is about 250 delegates short of the magical figure of 1,237 delegates, which is necessary for him to be the partys presidential nominee.
According to The Wall Street Journal, more Republicans are slowly beginning to express support for him.
Trump's early congressional backers, who initially faced scorn for backing the businessman are finding themselves in a more comfortable position, it observed.
"You're not having to stick your neck out quite as far as a few months ago. It's less of a stretch now. People like to be with the winner," Congressman Duncan hunter told the journal.
He was one of the few GOP lawmakers to endorse Trump in March.
A day earlier, Senator Bob Corker Chairman of the Senate Foreign Relations Committee welcomed the foreign policy speech of Trump.
"Today, Donald Trump delivered a very good foreign policy speech in which he laid out his vision for American engagement in the world," he said in yet another indication of the changing views of the top party leadership.
"Two weeks ago, people were telling me about Donald Trump's issues or negatives. Now they're reaching out, I want to support him, I'm going to support him, help me understand...there's definitely a mood shift, an energy shift," Congressman Chris Collins said after a meeting between Republican lawmakers and Trump campaign official.