A GOP congressman who said Saturday that President Donald Trump “engaged in impeachable conduct” reiterated his case Monday on Twitter.

Over the weekend, Rep. Justin Amash (R-Mich.) said on Twitter that after reading the complete Mueller Report, he believes Trump “engaged in specific actions and a pattern of behavior that meet the threshold for impeachment.”

Naturally, Amash’s comments angered the president, who called the congressman “a total lightweight.” In addition, Sen. Mitt Romney (R-Utah) called the congressman “courageous,” but said he does not think impeachment “is the right way to go.”

Amash’s comments even inspired a fellow Michigan Republican to mount a primary challenge against him.

On Monday, Amash answered his critics with another series of tweets, firing back against the arguments proffered by those saying the president should not be impeached.