Former Massachusetts Gov. Bill Weld officially announced his candidacy for the president of the United States on Monday, becoming the first Republican to challenge President Donald Trump for the 2020 election and opening up the possibility for a Republican primary.

John King, CNN’s chief national correspondent and host of "Inside Politics," told Boston Public Radio Tuesday that he didn't have much faith in Weld's ability to unseat Trump.

"There is zero evidence on the table at this moment that [the] president can be beaten in a Republican primary," King said. "I would not run to Vegas to bet on Weld to knock out President Trump in a Republican primary."

Read more: Bill Weld: 'It's Pretty Obvious That A Lot Of Things Need Doing In Washington That Are Not Being Done'

With little hope of winning, King believes that Weld's campaign is either about placing himself in a good position if the president is brought down by something like the Mueller report or one of the Democrat's subpoenas, or that he has entered the race to help stir Republican debate.

"It will be interesting to see the how and why later," King said about Weld's decision to run.

The 2016 election and the ups and downs of Trump's administration, though, has taught King not to count out the impossible.

"In the age of Trump, I keep an open mind about everything," he said.