A Republican congressman on Monday said Donald Trump and his press secretary, Sean Spicer, spent the weekend “derailing” the President’s core message with too much emphasis on things like inaugural crowd size.

Rep. Adam Kinzinger (R-IL) told CNN’s Ashleigh Banfield that there was “a big danger” of Trump losing the support of congressional Republicans with his remarks.

Kinzinger said that he “didn’t understand” Trump’s remarks Saturday in front of the CIA’s Memorial Wall and Sean Spicer’s first remarks as White House press secretary, both focused on the size of the inaugural crowd.

“It’s taking the message you want as a new President and it’s derailing it,” he said. “You’re in front of the CIA, this hallowed ground where it’s honoring people that have died on behalf of their country, and you barely mention it. I was disappointed in that.”

“Sean Spicer comes out and argues about crowd size. Look, the fact is you had a huge amount of people who were there and watching it on TV,” he continued. “But to get into the battle of, ‘No you’re not right about crowd size’ has nothing to do with the legacy of President Trump’s or what he’s going to do.”

Kinzinger said that Trump’s staff needed to “push back” against such statements in the future.

“From what I understand, Trump likes to be pushed back against. He likes people in his inner circle to fight back. He may need a little more of that when his reaction may be ‘I’m going to go give a speech at the CIA wall about crowd size,’” he said. “He needs someone to push back and say, ‘Mr. President, we’re not going to do that.’”

“Obviously it was a rough start, but let’s see how this week transpires,” he said. “From a messaging perspective, they’re going to have to get themselves way more disciplined.”

The congressman also noted there was “a big danger” of isolating congressional Republicans if Trump continues, in Banfield’s words, “muddying the waters,” and “getting into fights, perhaps, that he should not.”

Watch the exchange below: