The Human Rights Campaign (HRC), the nation's largest LGBT rights advocate, has endorsed Senator Susan Collins' Democratic challenger, Sara Gideon.

HRC made six candidate endorsements on Wednesday. In addition to Gideon, HRC endorsed Theresa Greenfield in Iowa, M.J. Hegar in Texas, John Hickenlooper in Colorado, and Jon Ossoff in Georgia, as well as the re-election campaign of Massachusetts Senator Ed Markey.

HRC has previously endorsed Collins, a Republican, three times.

In announcing the endorsements, HRC President Alphonso David cited the need to pass the Equality Act, an LGBT protections bill that cleared the House but stalled in the Republican-led Senate. Collins and Markey were co-sponsors of the legislation in the Senate.

“Despite support from 70% of the American public, Mitch McConnell has stood in the way of progress for LGBTQ people and refused to even allow a vote on the Equality Act,” said David in a statement. “Today’s endorsements mark the next step of HRC’s efforts to elect a pro-equality U.S. Senate and end McConnell’s tenure as majority leader. Each of these candidates are true allies of our movement and will work to ensure LGBTQ people are treated with the respect and dignity every human deserves. Together, united like never before, we can achieve the change our community needs.”

Speaking with the Washington Blade, David said that while Collins was a strong ally to the LGBT community, she remained in lockstep with Republican leadership on many critical issues.

“We are fighting for our lives and the only way to advance LGBTQ equality through the United States Senate is to install a new pro-equality majority leader and replace Mitch McConnell,” David said. “Despite Susan Collins’ record of support on certain key LGBTQ issues, her support of Mitch McConnell and Donald Trump’s agenda, endorsement of Brett Kavanaugh’s appointment to the Supreme Court and failure to hold Donald Trump accountable, is simply untenable.”

David was referring to Collins' vote to acquit President Donald Trump in February. Her vote also angered Republican groups opposed to Trump, such as The Lincoln Project.

A spokesperson for the Collins campaign chided HRC for its decision, saying that “this is not how you treat a friend and ally.”