Republican congressman: Donald Trump has gone 'off the track,' don't expect me to endorse

Michigan Rep. Fred Upton said Friday that he will not endorse presumptive Republican presidential nominee Donald Trump.

In an interview with a local radio station, Upton said that the brash billionaire has gone "off the track."

"Not a lot of happy campers in how this race is proceeding thus far," the Republican congressman said.

Upton is part of a growing list of conservatives who have refused to endorse the Manhattan real-estate mogul. Ohio Gov. John Kasich, Sen. Lindsey Graham, and Sen. Jeff Flake have all refused to throw their support behind Trump so far.

"There's a lot of things that folks are not happy about with either of these two candidates," Upton said. "We're running our own race, and don't look for me to endorse anyone in this race probably the rest of the year."

Upton is the chairman of the House Energy and Commerce Committee.