Trump had refused to rule out a third-party run during the Aug. 6 Republican debate.
NEW YORK -- Donald Trump will sign a pledge to back the Republican presidential nominee and not to run as an independent should he not win the party's nomination, multiple outlets have reported.
01:03 Trump’s Tax Plan: Low Rate for Corporations, and for Companies Like His17
23:38 Trump scrambles to show progress as the 100-day mark approaches18
19:00 Trump to meet with Australian prime minister on May 4: White House16
12:02 Trump Signals Shift on Wall Funding to Avert Government Shutdown33