'Gone astray': Republican dismayed as Trump turns back on 'America First' pledge

President Donald Trump's strike on Iran was a complete betrayal of what his supporters were voting for, Rep. Thomas Massie (R-KY) argued to MSNBC's Chris Hayes on Monday night.

Massie, a libertarian who frequently frustrates House GOP leadership with his votes against major party priorities, appeared on "All In" alongside Rep. Ro Khanna (D-CA). The two have introduced a War Powers Resolution to prohibit further action in Iran.

"Let me ask you that, Congressman Massie," said Hayes. "I mean...