Will Trump sign GOP loyalty pledge and rule out third-party run?

The pledge asks candidates to endorse the 2016 Republican nominee 'regardless of who it is,' and also to promise not to mount a third-party bid for the presidency should they lose the nomination.

Republican presidential candidate Donald Trump listens during a news conference in Greenville, S.C., Aug. 27, 2015.

Richard Shiro/AP

September 3, 2015

Donald Trump is set to meet with Republican National Committee chairman Reince Priebus Thursday afternoon in New York City, after which he is expected to rule out a third-party bid for president.

The meeting and anticipated announcement comes a day after party officials began circulating a loyalty pledge to all 17 major GOP candidates that appeared squarely aimed at boxing in Mr. Trump. The pledge asks candidates to endorse the 2016 Republican nominee "regardless of who it is," and also to promise not to mount a third-party bid for the presidency should they lose the nomination.

According to reports, signs indicate that the billionaire businessman who upended the race with his surprise candidacy will sign the pledge not to run as an independent.

Trump, was of course, the only candidate who, at last month's GOP debate, did not pledge he would not seek a third party run if he did not win the party's nomination, but after meetings with Mr. Priebus and party officials, reports indicate he may have changed his mind.

Whether or not he signs the pledge is significant. If Trump does mount a third party run, he will almost certainly siphon enough votes away from the Republican nominee to hand Democrats the victory.

As such, getting Trump to sign the pledge would be a coup for the RNC.

It could also help legitimize Trump, who has recently come under fire for not being a "real Republican." In recent days, rival Jeb Bush released an attack ad titled "Liberal things that Trump says," designed to shred Trump's conservative credentials. Signing the loyalty pledge could help bolster his credibility.

For his part, Trump hasn't indicated what decision he'll make.

14 Republicans running in 2016

On Saturday, he said, "We're going to make a decision very soon," reported the Associated Press, "and I think a lot of people are going to be very happy."

After meeting with Priebus at 1:30, Trump will hold a 2 p.m. news conference at Trump Tower to announce his decision. 

But here's the catch: Even if Trump signs the pledge, it is not legally binding, so it won't rule out a surprise third-party run.