Mr. Trump, who lost Massachusetts by 33.5 percentage points in the 2020 general election, attended a tele-rally for Mr. Diehl on Monday, declaring that Mr. Diehl would “rule your state with an iron fist” and push back on the “ultraliberal extremists.” Mr. Doughty, for his part, has campaigned with moderates like Gov. Chris Sununu of New Hampshire and was endorsed by the editorial board of The Boston Globe in the primary.
“President Trump still has a powerful message and an impact on politics in Massachusetts,” said Jim Lyons, the chairman of the Massachusetts Republican Party, which formally backed Mr. Diehl. “The results tonight will certainly give us an indication” of just how powerful, at least with Republican voters, he said.
Mr. Diehl was the overwhelming favorite at the state Republican convention. If he prevails, his primary victory will be the latest sign that Mr. Trump has refashioned the Republican Party in his image up and down the ballot and across the country, including in the Northeast, where moderate Republicans long thrived even as they shrank in number. Indeed, Mr. Baker, who defied Mr. Trump during his time in office and carved out a distinctive brand, has topped lists as the most popular governor in the country.
On the other side of the aisle, Democratic-leaning women, in particular, have appeared especially energized since the overturning of Roe v. Wade earlier this summer.
Ms. Healey, bolstered by a raft of endorsements from liberal organizations, labor and the political establishment, has had the field to herself since State Senator Sonia Chang-Díaz exited the primary contest in June, although Ms. Chang-Díaz was still listed on the ballot. That has given Ms. Healey a significant runway to focus on the general election and to engage in down-ballot races.
Ms. Healey, who was a college basketball captain at Harvard and played on a professional team overseas, has often used discussion of sports in her campaigns. In her Twitter bio, she describes herself as, among other things, a “baller.”