Gov. Doug Burgum, a former rival, endorses Donald Trump on eve of Iowa Caucus

North Dakota Gov. Doug Burgum, a former rival for the GOP presidential nomination,  endorsed Donald Trump Sunday and gave the former president a boost on the eve of the Iowa Caucus.

Burgum, who became the first of Trump's former GOP rivals to endorse him for president, joined Trump on stage at a campaign rally Sunday. 

"Four years ago, I was speaking on behalf of President Trump at the Iowa caucuses in Sioux City, and today, I'm here to do something that none of the other presidential primary candidates have done," Gov. Burgum said. "And that's endorse Donald J. Trump for the president of the United States of America." 

Trump is leading nationally in all the polls, including a double-digit lead in the final Iowa survey before Monday's vote.