Sam Donaldson isn’t buying into the notion that a Republican-controlled Senate would never vote to convict President Donald Trump if he’s impeached.

While few GOP lawmakers have shown any indication of abandoning the president, the longtime TV journalist told CNN’s “Reliable Sources” that could change in a hurry ― in one set of circumstances. If polls keep trending toward impeachment, Trump won’t be able to count on Senate Republicans to save him, he said.

Donaldson pointed to a Fox News poll released last week that found 51% want Trump impeached and removed from office, up from 42% in July.

“If it continues to rise, Mitch McConnell will throw him over,” Donaldson said in comments posted online by Mediaite. “These Republicans will suddenly decide, ‘We’ve been conned! How could we be fooled?’”

He added:

I’m telling you something, if public opinion is strongly for the impeachment and the conviction of President Trump, he will be convicted in the Senate with the Republican help.

Donaldson also offered some advice for journalists covering Trump: