Former San Francisco Mayor Willie Brown warned Democrats that pushing for President Donald Trump’s impeachment could backfire.

“As tempting as it is for the Democrats to push the idea that Trump could be guilty of obstruction of justice and push for impeachment, that could ultimately backfire on them—it raises public expectations, but if it doesn’t happen, it looks like you tried to do something and failed,” Brown wrote in his San Francisco Chronicle column over the weekend. “That wouldn’t just hurt the party this time. If a real Trump scandal comes along, the Democrats will be haunted by a decision to spend their political capital and credibility on a scandal that came up short.”

The legendary California Democrat said the “facts are not there” yet to make the case for impeachment. He added that former FBI director James Comey’s testimony “was great entertainment, but for all the hype,” the Senate Intelligence Committee hearings did not “deliver a knockout punch.”

“You are not going to get another ‘All the President’s Men’ out of this story,” he said, adding that “so far, there is no silver bullet that will bring the president down.”

California Democrats like Reps. Brad Sherman (D-CA) and Maxine “Get Ready for Impeachment” Waters (D-CA) have been leading the charge for impeachment. Rep. Ted Lieu (D-CA) has publicly stated that he is reading up on impeachment. And potential gubernatorial candidate and liberal megadonor Tom Steyer has also called for Trump’s impeachment.

Brown’s advice to Democrats: “Let the questions hang out there in the public’s mind, and leave the speculation to MSNBC.”