Republican US presidential candidate Donald Trump departs after a rally with supporters in Billings, Montana, US, May 26, 2016. [Photo/Agencies]

WASHINGTON - Brash US billionaire Donald Trump on Thursday hit the number of delegates needed to grab the Republican Party (GOP) nomination, as some experts predict that he will be a competitive candidate in the presidential race.

The development comes on the heels of Trump's recent surge in the polls, as he for the first time is running neck-in-neck with likely Democratic nominee Hillary Clinton. This foreshadows a tight contest in this year's race to the White House.

Just six months ago, most political observers dismissed Trump as a flash in the pan, but he now stands out as the winner in the Republican nomination fight.

And, for the first time, Trump recently inched ahead of Clinton in the Real Clear Politics polling average, although Clinton later moved ahead by a point. But with a margin of error around 2 points, the candidates are essentially tied.

"Trump has gotten a polling bump from nailing down the GOP nomination," Brookings Institution Senior Fellow Darrell West told Xinhua.

"Party leaders are endorsing him and he has made tremendous progress in unifying the Republican party. This is helping him greatly in the fall campaign against Hillary Clinton. As of right now, he has a more unified party than she (Clinton) does," he said.

Dan Mahaffee, an analyst with the Center for the Study of the Presidency and Congress, told Xinhua that a lot of the GOP establishment and voters are beginning to unify behind Trump despite concerns about specific policies.

Once it became clear that after former GOP candidates Senator Ted Cruz and Ohio Governor John Kasich quit the Republican nomination race in early May, many establishment Republicans who had in the past expressed a dislike for Trump began to rally around him.