Donald Trump Considering Taking Pledge Not to Run as Third-Party Candidate

— -- UPDATE: GOP frontrunner Donald Trump told ABC News Monday he has no imminent plan to rule out a third-party run for president. “It’s absolutely possible that at some point I would change that,” Trump told ABC News over the phone, but, he added, such a change “is not imminent.” Read more here.

Donald Trump may soon do what Republican leaders have been asking the billionaire candidate to do -- pledge not to run as an independent candidate for president, a senior Trump adviser told ABC News.

Trump refused to take that pledge at the start of Thursday's GOP debate but is now seriously considering promising not to run as an independent if he does not win the Republican nomination, the adviser said.

Trump has repeatedly said he wants to run as a Republican and expects to win the GOP nomination, but he has also insisted that if he is not treated well by party leaders and does not get the nomination he may run as an independent.

Republican National Committee Chairman Reince Priebus has directly called on all candidates to pledge not to make a third-party run. The Republican Party has leverage here: senior GOP officials say it is possible that future debates could be limited to candidates who have pledged support for the party -- a move that could leave Trump out of debates if he is still leaving open the possibility of running as an independent.

The RNC has already made it clear that it will withhold valuable party data on Republican voters from any candidate unwilling to pledge support to the party.

Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here. To be notified about our live weekend digital reports, tap here.