Former Massachusetts Gov. William Weld (R) rejoined the Republican Party as he considers a primary challenge to President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE in 2020.

Weld changed his party registration from Libertarian back to the GOP Tuesday, according to The Associated Press.

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Weld served as the Bay State’s governor from 1991 until 1997. He later registered with the Libertarian Party and ran for vice president with former New Mexico Gov. Gary Johnson Gary Earl JohnsonWhat the numbers say about Trump's chances at reelection Presidential race tightens in Minnesota as Trump plows resources into state The Hill's Campaign Report: Biden condemns violence, blames Trump for fomenting it l Bitter Mass. primaries reach the end l Super PAC spending set to explode MORE in 2016.

Weld raised eyebrows last week when he told WMUR last week that he would discuss any presidential plans during an upcoming visit to New Hampshire.

“Bill Weld ran as a Libertarian candidate for vice president,” Stephen Stepanek, the chair of the New Hampshire GOP and the Trump campaign’s 2016 New Hampshire co-chair, told WMUR. “He’s a Libertarian and if he wants to run for president as a Libertarian, that’s fine. But we don’t want him back in the Republican Party.”

Former Ohio Gov. John Kasich (R) and Maryland Gov. Larry Hogan (R) are also considering primary challenges to Trump in 2020.

The AP reported Monday that the Trump campaign is taking steps to minimize the possibility the president could face a Republican challenger next year, working to change state party rules, issue endorsements and lobby state officials to ensure only Trump appears in GOP primary contests.

Regardless, Trump would likely not face any significant challenge to his nomination in 2020 as he has solidified his grip over the GOP base since his inauguration. While primary challengers can certainly pester sitting presidents, as Pat Buchanan did in 1992 with President George H.W. Bush, none in recent history have ever beaten out the incumbent for their party’s nomination.