Gov. Janet Mills on Tuesday stopped short of endorsing her party’s nominee, Democrat Troy Jackson, for U.S. Senate.

Instead, Mills focused on her party’s mission: giving the old Bean Boot to Susan Collins, the five-term Republican incumbent.

“Susan Collins is vulnerable and she should be defeated,” Mills told reporters after an event in Dresden in which she declared this upcoming weekend “Wild Blueberry Weekend.”

Mills didn’t explicitly rule out a future endorsement of Jackson. Such moments are usually done in coordination with a campaign, and the governor said she had not yet spoken to Jackson since he became the nominee last week.

But the episode begs the question: Would Jackson benefit from a Mills endorsement?

Mills was forced out of the Democratic Senate primary in April. She was trailing in the polls and lagged in fundraising. And recent polling shows her favorability ratings underwater. But the midterms are an all-hands-on-deck moment for Democrats looking to defeat Collins.

Jackson’s campaign didn’t address whether he would seek or accept Mills’ endorsement when asked about it on Wednesday.

“Troy worked with Governor Mills to pass some of the most progressive abortion rights legislation in the country,” a campaign spokesperson said in a written statement. “This campaign is going to take everyone coming together to beat Susan Collins, and we’re confident Mainers will do just that.”

This week, Jackson was endorsed by former Vice President Kamala Harris.

A New York Times/Portland Press Herald/Siena poll conducted in June, when Graham Platner was the Democratic nominee, showed Mills’ favorability at minus-8 percentage points. That was worse than Collins, who was also underwater at minus-2 points.

That poll didn’t test Jackson’s favorability, since at that point he had lost the governor’s primary and Platner had not yet dropped out of the Senate race. But a separate survey by the University of New Hampshire Survey Center earlier this month showed Jackson’s favorability above water — at plus-5 points.

Despite these ratings, Jackson’s campaign statement at least left the door open to accepting an endorsement by focusing on areas in which Mills and Jackson agreed when he was president of the Maine Senate.

In addition to expanding abortion access in 2023, Jackson helped Mills broaden the MaineCare program right after she took office in 2019. And they worked together to provide free meals to public school students and bolster the childcare industry here.

But Jackson’s campaign statement also marks a shift in tone from Democratic gubernatorial primary, when he sought to distance himself from the governor. (Mills endorsed Hannah Pingree, the eventual Democratic nominee, in that race.)

Mills and Jackson had numerous policy disagreements during the latter’s six years as senate president.

During a televised debate in May, Jackson noted that Mills had vetoed 40 of his bills. He pointed to a specific measure to limit the price of prescription drugs.

“She said big pharma was going to sue us,” Jackson said, adding that a similar measure has since been implemented in Colorado. “Big pharma always sues. That’s their business model.”

Jackson also supported sweeping bills to recognize tribal sovereignty. Mills opposed those broad efforts in favor of more incremental reforms — a position that infuriated progressives.

Jackson also sought to expand the power of labor unions, including bills to benefit farmworkers. He sponsored a bill that would have made arbitration binding on wages and other issues during an impasse in contract negotiations. But those efforts were often opposed by the state’s chief executive, who has been the subject of several labor complaints from state unions.

There were also regular disagreements over state budgets. Jackson wanted higher spending levels, given historic state revenues. But Mills worried about an economic downturn and urged her party, which controls both chambers, to show fiscal restraint.

While some of those disagreements happened behind closed doors, they occasionally spilled into public. So much so that in 2021, a progressive political action committee, Run Troy Run, tried to draft Jackson to run against Mills in the 2022 governor’s race.

Jackson dismissed the effort, and endorsed Mills, his party’s leader in the state.