NEW YORK (Reuters) - Republican front-runner Donald Trump on Thursday bowed to pressure from the party establishment and signed a pledge not to run as an independent candidate in the November 2016 presidential election.
His vow of loyalty was something of a victory for the Republican National Committee in its efforts to rein in the billionaire, who leads opinion polls while at the same time upsetting mainstream Republicans with his brash style.
But the pledge does not appear to be legally binding and does nothing to halt Trump's personal attacks against Republican rivals and stinging rhetoric on issues like immigration that have shaken up the race for the nomination.
At a news conference in his own Trump Tower in Manhattan,
the property magnate waved the loyalty pledge, signed in a thick black marker, in the air for TV cameras.
"I see no circumstances under which I would tear up that pledge," he said.
Trump had previously refused to rule out a third-party bid, drawing boos from the crowd in Ohio last month at the first full Republican debate.
An independent Trump candidacy could split support for the Republican Party and give the Democrats a huge boost by taking
many blue-collar male Republican voters with him.
He said on Thursday he received "absolutely nothing other than the assurance that I would be treated fairly" in return for signing the pledge.
The reality TV star had come under intense pressure in recent weeks from the RNC and its chairman, Reince Priebus, who met with him on Thursday.
"It reflects a lot of behind the scenes work," an RNC official said.
Priebus announced in a statement later on Thursday that all 17 Republican candidates had agreed to the pledge.
Trump may also have been reacting to goading from rival Jeb Bush, who this week released a video accusing him of being a Democrat in disguise and holding liberal positions on abortion rights, taxes and healthcare.
"I don’t know what motivated (Trump) specifically, but the problem is that it’s a non-binding deal," said Dave Carney, an unaligned Republican strategist in New Hampshire. He said the pledge had some meaning during the primary process, which is run by state parties, but not during the general election, which is organized by state governments.
Almost two months after reaching the top of opinion polls among Republicans, Trump has come under sustained fire for the first time from Bush, the former governor of Florida.
Reuters/Ipsos polling showed Trump with support among nearly 31 percent of self-identified Republicans as of Tuesday, with Bush at nearly 12 percent, behind former neurosurgeon Ben Carson. bit.ly/1hWTSGh
Trump fired a salvo back on Thursday in a fight with Bush over immigrants and the role of English.
"I think that when you get right down to it, we're a nation that speaks English and I think while we are in this nation we should be speaking English," he said. "Whether people like it or not, that's how we assimilate."
In turn, Bush made fun of Trump's pledge by tweeting a photograph of a piece of paper with the words "Voted Republican since 1972," on it and signed by Bush.
Political parties at the state level often ask candidates to sign loyalty pledges, but it is unprecedented for Republicans in a presidential election.
Another of the Republican candidates, New Jersey Governor Chris Christie, said the Trump pledge was "just a little too much drama."
Additional reporting by Alistair Bell and Alina Selyukh in Washington and Steve Holland in Hampton, N.H.; Editing by Cynthia Osterman and Peter Cooney