Massachusetts Has a Primary on Tuesday. Here’s What to Watch.

Three Republicans are vying Tuesday to take on Ms. Warren, who has no challenger in the Democratic primary and has already raised more than $31 million. The Republicans are: State Representative Geoff Diehl; Jon Kingston, a business executive; and Beth Lindstrom, a long time Republican operative and former cabinet official under former Gov. Mitt Romney.

Mr. Diehl has long supported President Trump, while the other two have not. It is not clear how much weight that might carry in this primary. As for November, Mr. Trump lost Massachusetts in 2016 by 27 percentage points. (Read more here about how the president’s endorsements have shaped Republican primaries.)

Other key contests to watch

In the race for governor, the incumbent, Charlie Baker, a Republican who polls say is the most popular governor in America, is expected to fend off a primary challenge from Scott D. Lively, a far right pastor.

Two Democrats — Jay M. Gonzalez, a cabinet member under former Gov. Deval Patrick, and Bob Massie, an environmental activist — are vying for the chance to run against Mr. Baker in November.

In two other House districts, younger women are challenging long-serving male incumbents in the Democratic primary.

In the First, in Western Massachusetts, Representative Richard Neal, first elected nearly three decades ago, is being challenged by Tahirah Amatul-Wadud, a black Muslim civil rights lawyer.

In the Eighth, which covers parts of Boston and the South Shore, Representative Stephen Lynch, first elected 18 years ago, is facing a challenge from Brianna Wu, a video game developer. Also running in that primary is Christopher Voehl, a pilot.