"Warriors stand and fight for what they believe," wrote three of the president's Republican challengers.
"I’m not looking to give them any credibility," the president told reporters of his fellow Republicans Mark Sanford, Joe Walsh and Bill Weld.
"He’s nuts. He’s erratic. He’s cruel," former Rep. Joe Walsh said of the president. "He doesn’t give a damn about America.”
"We are in a fight for the soul of the GOP, and silence is not an option," the Republican presidential candidate said.
In an op-ed, former Massachusetts Gov. Bill Weld said the Mueller report proves that Trump is "a pathological liar."
Weld is the first major intra-party challenger against a sitting president since Pat Buchanan took on George H.W. Bush.
The former Massachusetts governor is the first — and so far, only — Republican to challenge the president in the 2020 primaries.
The former Massachusetts governor says there are plenty of other good reasons to oppose the president’s re-election, including ongoing state and federal probes.
Presidents who recently lost re-election bids all faced a primary challenger. The ex-governor wants the same for Trump.
Trump's widely expected veto would force congressional Republicans to choose between supporting him and defending their own constitutional powers.
The former GOP governor said Republican leaders "want to have no election... I don’t think that would be very good."
The move makes Trump the first incumbent president since George H.W. Bush in 1992 to face a notable primary challenge.
A Gallup poll from October shows that 64 percent of Americans favor making marijuana legal.
"She deserves to have people vouch for her other than members of the DNC, so I’m here to do that."
Weld is campaigning against Donald Trump.
"The rage that one felt was an abstract, undirected emotion which could be switched from one object to another like the flame of a blowlamp.”