Democrat Jay Gonzalez kept up his assault on Gov. Charlie Baker on Thursday over the Republican's endorsement of Geoff Diehl for U.S. Senate, hammering home Diehl's ties to a deeply unpopular President Donald Trump.

Democrat Jay Gonzalez kept up his assault on Gov. Charlie Baker on Thursday over the Republican's endorsement of Geoff Diehl for U.S. Senate, hammering home Diehl's ties to a deeply unpopular President Donald Trump.

Gonzalez and Democrats in the days since the primary elections have seized on Baker's support for Diehl, who was a leading surrogate for Trump's campaign in Massachusetts, as a wedge issue that could help energize a Democratic base eager to take action against the president ahead of the 2020 election.

"Make no mistake. By working to help Geoff Diehl, Charlie Baker is supporting Donald Trump's hateful and harmful agenda. He's backing an anti-choice, anti-LGBTQ, anti-immigrant, pro-NRA agenda. It's not Ok," Gonzalez said at Democratic Party headquarters.

A Morning Consult poll released Thursday showed support for Trump in Massachusetts at among the lowest levels in the country, with just 36 percent saying they approve of the president.

Baker has not said who he voted for in the three-way Republican primary for U.S. Senate, but backed into an endorsement of Diehl on Friday when he said he would be supporting the entire GOP slate in November. His campaign has since pointed out that Baker did not vote for Trump and has opposed his party in Washington when he disagrees with its agenda.

Gonzalez, however, brought in several State House lawmakers and the state director of the Sierra Club to help him make his case that Baker is trying to have it both ways.

Deb Pasternak, of the Sierra Club, said Trump's administration has rolled back clean air and water protections, and wants to ease restrictions on carbon emissions. "Were he to become senator, he would rubber stamp Donald Trump's agenda," she said of Diehl.

Diehl, in an interview with the News Service, said Gonzalez's focus on his relationship with the governor "seems to show his campaign doesn't have much to talk about."

"I provide a seat at the table that's going to be an asset for the governor," Diehl said, referencing the state's lack of Republican representation in Washington. Diehl also disputed the idea that he would be a "rubber stamp" for Trump, pointing out his opposition to the president's proposal to eliminate the state and local tax deductions as part of the GOP tax reform plan.

"I've certainly been willing to call out the president when he's wrong, just like I don't always agree with the governor," Diehl said. "I think people know who I am from my record long before working on the '16 campaign, whether it was working against the gas tax or pushing back against the Olympics."

Rep. Marjorie Decker, a Cambridge Democrat and the sponsor of a "red flag" gun law, said that Diehl voted against her bill that allows family and close friends to petition the court to have someone's guns taken away if they pose a threat. Baker, she said, signed the bill, but "did not do the heavy lifting" it took to get it passed.

"He didn't have to," Decker said about Baker's decision to endorse Diehl. "This would have been one of those moments to really show how he was different from Trump."

Both Decker and Somerville Rep. Christine Barber said they often collaborate with Republicans on Beacon Hill, but do not have much of a working relationship with Diehl.

"Geoff Diehl is someone who has a right-wing agenda, is not interested in bipartisanship, and is not someone who is easy to work with or interested in the issues I care about," Barber said.

Sen. Jamie Eldridge also attended to highlight Diehl's support for repealing the Affordable Care Act, which Baker has opposed.