Reince Priebus is never far from Donald Trump's side.

The outgoing RNC chairman and incoming White House chief of staff often joins Trump when he interviews candidates for his Cabinet in his cozy Trump Tower office. He accompanies Trump at high-level meetings, like their well-publicized dinner with Mitt Romney.

And he frequently makes jaunts with the president-elect in Trump's jet, from a victory rally in Priebus's native Wisconsin to a recent Army-Navy football game.

The consummate D.C. insider, Priebus has not just emerged as Trump's public liaison to a still-skeptical GOP establishment; the 44-year-old political operative has become a trusted adviser to and staunch defender of the president-elect, even as he competes for power and influence with rivals like Steve Bannon and Kellyanne Conway who were with Trump from the beginning.

Those who have been in the room with both Trump and Priebus say they wouldn't describe Priebus as deferential to his new boss. In fact, Priebus appears at ease with Trump. He doesn't hesitate to interject and offer his opinion, and the two often banter back and forth.

"Trump and Reince have a tremendous rapport with each other," said Rep. Kevin Cramer (R-N.D.), who observed the two men interact with each other at Trump Tower during his interview for Energy secretary this month.

"Trump's respect for Reince is very obvious. Reince was never disrespectful, but he never hesitated to jump right in. I was impressed."

The Wisconsin Republican's first month as Trump's chief of staff has been marked by successes, and a few setbacks.

Priebus failed to convince Trump that one of his most vocal critics during the campaign, 2012 GOP nominee Mitt Romney, should head the State Department.