Pro-Trump candidate Geoff Diehl triumphs in Massachusetts primary, to take on Elizabeth Warren in November

State Rep. Geoff Diehl won the primary to take on Sen. Elizabeth Warren in Massachusetts. (AP Photo/Winslow Townson, File)

Republicans in deep-blue Massachusetts selected pro-Trump State Rep. Geoff Diehl to take on incumbent Democratic Sen. Elizabeth Warren in November, setting the stage for a contentious referendum on the first-term senator's national profile as she openly mulls a run for the presidency in 2020.

Diehl triumphed over attorney John Kingston, and Beth Lindstrom, an aide to former Gov. Mitt Romney, with early results showing him with a convincing double-digit lead over his rivals.

Of the three candidates, Diehl had the closest ties to President Donald Trump. Diehl co-chaired Trump's 2016 Massachusetts campaign. He was quick to note that despite its liberal reputation, Massachusetts gave Trump one of his most lopsided early primary wins.

Warren, who has served in the Senate since 2013, ran unopposed in Tuesday's Democratic primary. She released ten years worth of tax returns recently, laying the groundwork for a potential presidential run in 2020.

Warren hasn't yet declared her intention to run, saying she's wanted to focus on her reelection first. But she has clearly floated the possibility of pursuing the White House, saying in August she's not afraid to be "the underdog."

President Trump repeatedly has unloaded on his prospective rival, saying she lied about having Native American roots to help her legal career and vowing to toss a heritage test at her during a presidential debate.

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Fox News has ranked the November race as likely Democrat.

Meanwhile, Massachusetts Republican Gov. Charlie Baker on Tuesday soundly defeated ultraconservative challenger Scott Lively on his way to seeking a second four-year term in office, overcoming charges that he is too moderate as Republicans seek to maintain their hold on New England's governorships.

He's set to face 47-year-old Ohio native Jay Gonzalez, the Democratic nominee for governor, in November. A former official in the administration of Democratic Gov. Deval Patrick, Gonzales has hammered Baker on the deficiencies in the state's mass transit system and called for stronger protections for immigrants.

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But despite Massachusetts' longstanding reputation as a deeply liberal state, Baker commands sky-high approval ratings there and ranks among the nation's most popular governors. He largely ignored Lively, a staunch supporter of President Trump.

Democratic Rep. Richard Neal flips a coin to determine speaking order as challenger Tahirah Amatul-Wadud looks on before their primary debate at WGBY TV in Springfield, Mass., Thursday, Aug. 30, 2018. (AP)

Baker credited in part his willingness to work cooperatively with Democratic leaders at the Statehouse. He is a progressive Republican, and supports universal healthcare and greater state investments in transportation and education.

Republicans currently hold the governorships of four out of six states in highly liberal New England, including Vermont, Maine, Massachusetts and New Hampshire, and are looking to grow that number in November.

Also on Tuesday, in a major upset, Boston city councilor Ayanna Pressley defeated 10-term incumbent Rep. Michael Capuano. Pressley, expected to be the first black woman elected to represent Massachusetts in Congress because she's set to run unopposed in November, had the backing of Democratic socialist Alexandria Ocasio-Cortez.

And Rep. Richard Neal defeated Democratic primary challenger Tahirah Amatul-Wadud, an attorney who had hoped to make history herself by becoming the first Muslim elected to Congress from Massachusetts. She backed a proposal to make Medicare available to all Americans regardless of age.

Neal will run unopposed in November.

Fox News' Samuel Chamberlain and The Associated Press contributed to this report.