One of President Trump's most ardent supporters fired a warning shot across the commander-in-chief's bow.

In an interview on Fox News, Former Speaker of the House Newt Gingrich called out the president for the gaffes he has made and the growing list of enemies he is creating in his first six months in Washington.

Gingrich said, "If the president wants to have a serious, stable presidency, he needs to enact serious changes."

Gingrich mentioned Trump's 1997 book the Art of the Comeback and noted, "he needs to take his own advice and start thinking about what isn't working. You don't get down to 35% and have people in your own party shooting at you and think everything is fine. I think he's in a position right now where he is much more isolated than he realizes."