PORTLAND — Planned Parenthood on Tuesday endorsed a Democrat hoping to challenge Republican Sen. Susan Collins of Maine, saying Collins “turned her back” on women and citing her vote to confirm Brett Kavanaugh to the Supreme Court as well as other judicial nominees who oppose abortion.

House Speaker Sara Gideon, D-Freeport, flashes a thumbs up at a Democratic colleague before the start of the first session of the new year Jan. 8 at the State House House. Associated Press/Robert F. Bukaty

Maine House Speaker Sara Gideon of Freeport welcomed the endorsement from the Planned Parenthood Action Fund. “There’s never been a more important time to stand up for reproductive rights,” she said, in the face of “systematic attacks on reproductive rights across the country.”

Collins, who was honored by Planned Parenthood as recently as 2017 as “an outspoken champion for women’s health,” is facing perhaps the toughest reelection fight of her career. Critics have vowed they won’t forget her key vote for Kavanaugh, whose nomination survived an accusation that he sexually assaulted someone in high school.

Sen. Susan Collins arrives at the Capitol on June 18 to extend her perfect Senate voting record to 7,000. Associated Press/J. Scott Applewhite

“From her decisive vote to confirm Kavanaugh to her refusal to stop Republican attacks on our health and rights, it’s clear that she has turned her back on those she should be championing,” said Alexis McGill Johnson, acting president and CEO of Planned Parenthood . She said Collins “has abandoned not only the people of Maine, but women across the country.”

The Collins campaign said Planned Parenthood has changed and become more partisan, noting that no Republicans have won its endorsement.

“Senator Collins has not changed, but leadership at Planned Parenthood certainly has,” Collins campaign spokesman Kevin Kelley said. “It’s sad that the group is now run by far left activists who would rather focus on partisan politics than bipartisan policies that provide health care to women.”

The endorsement was one of several announced Tuesday, the day before the anniversary of the landmark Roe v. Wade ruling that made abortion legal. The Planned Parenthood Action Fund also is backing Democrat Jaime Harrison, who’s seeking to unseat GOP Sen. Lindsey Graham of South Carolina, and Democrat Barbara Bollier, who’s running for an open Senate seat in Kansas.

In Maine, Collins and Planned Parenthood have had a complicated relationship.

Collins has supported funding for the organization, and she received its endorsement once before, in her 2002 reelection campaign. She was honored by the group in 2017 with its Barry Goldwater Award to a public official who has acted as a leader within the Republican Party to support Planned Parenthood.

“Senator Collins has been an outspoken champion for women’s health. Thanks to Senator Collins’ steadfast commitment to her constituents, tens of thousands of women in Maine and millions of women across the country still have access to essential health care,” Cecile Richards, then-president of Planned Parenthood Federation of America, said at the time, about a year before the Kavanaugh vote.

The relationship with the organization has gone downhill since then.

The 67-year-old Collins said Kavanaugh, who denied the sexual assault allegation, vowed to respect precedent including the Roe v. Wade ruling. But Planned Parenthood contends 26 proposals to limit abortions have been adopted in 17 states since then.

Gideon, meanwhile, supports Medicaid expansion and expanded health care for women and has vowed to continue “the fight to protect and expand reproductive rights.”

“As a former Planned Parenthood patient, she knows what it means to be able to get the care you need from a trusted provider and how hurtful it is to see your provider attacked by extremist politicians,” Nicole Clegg, of Planned Parenthood Maine Action Fund, said in a statement.

Money is already pouring into the Senate race. Collins is considered among the most vulnerable Republican senators in the nation, a new position for her in a state where rising polarization and partisanship is clashing with a culture of independence.

Gideon is backed by the Democratic Senatorial Campaign Committee. But she faces activist Betsy Sweet, attorney Bre Kidman, former Google executive Ross LaJeunesse and travel agent Michael Bunker in the Democratic primary.

Kidman expressed disappointment Tuesday, saying that when their team reached out they were told that Planned Parenthood Action Fund “intended to remain neutral in the primary.”

“As one of the first greeters at the Planned Parenthood health center in Portland, I physically protested patients’ rights to access reproductive healthcare in sun, rain, sleet, and snow — often bodily shielding people from encounters with protestors,” Kidman said in a statement.

Both Collins and Gideon already have raised millions of dollars for the race. Tracking firm Advertising Analytics projects that the candidates and outside groups will spend $55 million on ads by Election Day.