Former New Jersey Gov. Chris Christie gave his take Tuesday on how the Democrats could defeat President Trump in 2020.

His advice: Get behind a mayor or governor, not senators.

"They should not nominate anyone from the United States Senate," Christie said during an event for the Atlantic Festival in D.C.

"If you run a Washington insider against Donald Trump, I'm willing to bet you today that he will feed them their lunch," he said. "You need a governor or a mayor who has never been in Washington, who has actually run something that is governmental, who can get in there and say 'this, this, this, this, and this up — and I wouldn't.'"

Trump himself ran as an outsider candidate looking to shake-up Washington. He defeated a wide array of GOP rivals in the 2016 primaries that contained senators and governors, including Christie himself.

Taking a survey of the current field of top potential contenders for Democrats, Christie surmised that their base is getting excited about the wrong people.

"Unfortunately for them, I think that the people that are emerging at least for the moment are all kind of the class of senators that are all out there killing each other," he said.

Christie didn't mention specific names, but a number of senators have been talked about as leading prospects, including Elizabeth Warren of Massachusetts, Kamala Harris of California, and Cory Booker of New Jersey. Harris and Booker, who are both members of the Senate Judiciary Committee, in particular have grabbed headlines in recent days with their vocal objections to the nomination of Brett Kavanaugh to the Supreme Court.

There are some state and local officials also in the mix, including former New York Mayor Michael Bloomberg, Former Virginia Gov. Terry McAuliffe, Former Massachusetts Gov. Deval Patrick, and New Orleans Mayor Mitch Landrieu.

Kavanaugh is now facing an FBI inquiry into the allegations he denies. The full Senate isn't expected to vote on his confirmation until the investigation has completed.

Christie, a former adviser of Trump's who is now an ABC contributor, further noted Tuesday that Trump's brashness has tempted rivals into wanting to be "outrageous." But, he warned, "No one can be as outrageous as him."