WASHINGTON, Sept. 3 (Xinhua) -- U.S. billionaire developer and reality show celebrity Donald Trump has multiple identities. But his newest was unveiled Thursday.

To the great relief of the Republican leadership, Trump signed Thursday a loyalty pledge saying he will only run as a Republican candidate in the 2016 election, ruling out the possibility that he will run a third-party campaign if losing the party's nomination.

"I will be totally pledging all my allegiance to the Republican Party and the conservative principles to which it stands," said Trump at a press conference in New York.

"We will go out and we will fight hard and we will win, and most importantly, we will make our country great again," said Trump to his cheering supporters.

Trump's pledge of not running a third-party bid ended a month-long drama climaxing with his public defiance of such a pledge on Aug. 6 in front of about 24 million TV viewers during the first Republican presidential primary debate.

For the Republican National Committee (RNC), which sent out written pledges to Republican candidates on Wednesday, Trump's pledge matters more than others.

Standing atop almost every national poll for months, with a double-digit lead over the crowded Republican field, Trump's popularity shows no trace of ebbing away.

Trump's Republican critics and rivals, initially baffled and now resigned, had a hard time in the passing summer, with Trump sucking up media and political oxygen and setting Republican primary agenda literally on his own.

Unfortunately, the bitterness of running against Trump is more likely to stretch into the upcoming fall, winter, and probably even next spring.

While the scenario of Trump winning the party's nomination still remains fictional for many, his previous threats of running independently because the RNC "is unfair to him" jangled the nerves of many.

Previous polls indicated that if Trump were to run as an independent, he would distract substantial support from the Republican nominee and almost certainly hand over the White House to the Democratic Party.