Trump has an 89 percent job approval rating among Republican voters, a recent Gallup poll shows.
Bill Weld, the former governor of Massachusetts, said on Tuesday he's running in 2020 as a Republican because he wants a "direct shot" at President Donald Trump.
"I want a direct shot at the man who, I think, wishes our country ill," Weld said on MSNBC. "The best way to get a direct shot is to run against him in his own party."
Weld, who served as a Republican governor and ran as a vice presidential candidate for the Libertarian Party in 2016, said he wants to restore civility to political discourse and challenge Trump's domestic and foreign policies.
"Everyone knows the president is mean-spirited and that he calls out little people by name. ... The more that's known about the president's business conduct and his conduct in office, the more I think people are going to come to question whether they really think it's such a great idea being behind this commander in chief in office," he said.
Weld said he believes much of Trump's support is steered by "party bosses" in state GOP committees, but he wants to talk directly to Republicans voters about Trump's conduct and his policies.
"We want to the election, both the primary and general, decided by voters and not party bosses," he said. "I think what (voters) are saying is they are buffaloed and they want to stick with the Republican Party because they like the way it feels. I don't think they've examined the president's conduct."
Weld said he and Trump differ on "many, many" issues; Weld said he is an "economic conservative" who has a track record of cutting spending and taxes in Massachusetts. He said the president has demeaned America's allies and his economic policies have not been good for the country.
"I aim to call the president out on issues like spending and insulting our allies," he said.
But, Weld said he has one thing in common with the president.
"We're both big, orange men," he said.
Primary challenges sometimes precede losses for presidents whose approval ratings have dipped in the run-up to elections. Conservative pundit Pat Buchanan challenged President George H.W. Bush to the Republican nomination in 1992. Bush ultimately lost that general election to Bill Clinton. Ronald Reagan challenged President Gerald Ford in 1976. Ford lost to Jimmy Carter in the general election.
Trump remains deeply popular with Republican voters, however. A recent Gallup pollshows that the president has an 89 percent job approval rating among Republican voters, and a 45 percent approval rating overall. Trump's reelection campaign also raised more than $30 million in the first quarter of 2019, far outpacing the field of Democratic candidates heading into the 2020 race.