BOSTON (AP) — Democratic U.S. Sen. Elizabeth Warren will face off against Republican state Rep. Geoff Diehl as she battles for a second term and gears up for what could be a possible run for president.

Diehl defeated two other GOP candidates in Tuesday's Massachusetts primary for the chance to unseat Warren in November, beating back business executive John Kingston and Beth Lindstrom, a Cabinet official under Republican Gov. Mitt Romney.

Diehl told supporters Tuesday that he was proud to be the GOP nominee and will work hard to represent Massachusetts in the Senate.

"It all comes down to this," Diehl said. "While Warren has spent the last six years building a national political profile for herself, I've been fighting for you."

Warren ran unopposed in the Democratic primary and said she will fight her heart out to win re-election.

"This campaign has never been just about me," Warren tweeted. "It's been about all of us fighting to level the playing field for working people."

Diehl has close political ties to President Donald Trump, having co-chaired Trump's 2016 Massachusetts campaign. Diehl has noted that Massachusetts gave Trump one of his most lopsided early primary wins.

Diehl has also tried to turn Warren's national profile against her, criticizing her for being too politically extreme and spending too much time preparing for a possible presidential run in 2020.

Warren, 69, routinely spars with Trump on Twitter. She's also a standard-bearer in the resistance to the Republican administration and recently released 10 years of tax returns — a move seen as another possible step to a presidential bid. Trump has refused to release his tax returns.

Warren has said she's not running for president.

Whatever vulnerabilities Warren may bring to her re-election bid, any Republican faces tough odds in Massachusetts, where GOP voters make up less than 11 percent of the electorate and where Trump is so unpopular, Republican Gov. Charlie Baker couldn't bring himself to vote for him in 2016.

Lindstrom, 56, and Kingston, 52, were more reluctant to fully embrace the president than the 49-year-old Diehl.

There were many areas where the three GOP challengers agreed. Each praised Trump's decision to nominate Judge Brett Kavanaugh to the U.S. Supreme Court and criticized Warren's opposition as a knee-jerk liberal reaction. They also voiced support for the tax plan approved by Congress and signed by Trump. Warren has described the measure as a "tax giveaway to giant corporations and the super-rich."

All three also condemned Warren's comments on the death in Iowa of 20-year-old Mollie Tibbetts and the suspect charged with first-degree murder — a native of Mexico suspected of being in the U.S. illegally. Warren had expressed sympathy for the young woman's family and added: "But one of the things we have to remember is we need an immigration system that is effective, that focuses on where real problems are." Warren said she met mothers separated from their children at the border and "we need immigration laws that focus on people who pose a real threat."

Diehl criticized the comments and said Warren should back off calls to abolish Immigration and Customs Enforcement, the federal agency also known as ICE.

All three, including Diehl, said they wouldn't use the term "Pocahontas" to refer to Warren. Trump has repeatedly used it to denigrate Warren's claims of Native American heritage.