Sen. Susan Collins Susan Margaret CollinsSenate Republicans face tough decision on replacing Ginsburg Democratic senator calls for eliminating filibuster, expanding Supreme Court if GOP fills vacancy What Senate Republicans have said about election-year Supreme Court vacancies MORE (R-Maine) is being challenged on her vote to confirm Supreme Court Justice Brett Kavanaugh Brett Michael KavanaughProgressive group to spend M in ad campaign on Supreme Court vacancy Senate Republicans face tough decision on replacing Ginsburg Trump reacts to Ginsburg's death: 'An amazing woman who led an amazing life' MORE in a new six-figure digital ad campaign launched Tuesday by the progressive group Demand Justice.

The 30-second ad questions Collins’s history of saying she supports abortion rights in light of her vote for Kavanaugh.

“I used to support Susan Collins because I believed that she was a moderate and a voice of reason in the political realm,” a Maine resident named Amy, who identifies as a past supporter of Collins, says in the ad.

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“Her vote to confirm Judge Kavanaugh made me realize that Susan Collins was not true to her word when she said that she supported a woman's right to choose. It’s easy to say, and she says it often, but her actions don’t back up her words,” Amy continues.

This is the second Demand Justice ad featuring Amy.

Collins, a four-term senator, is facing her toughest election yet in November. Her race is ranked a “toss-up” by the Cook Political Report.

The same day the ad was announced, Planned Parenthood Action Fund announced it is endorsing Collins’s strongest Democratic challenger, Sara Gideon, who is currently serving as Speaker of Maine's House of Representatives.

Planned Parenthood had supported Collins, one of the few Congressional Republicans to support abortion rights, in the past, but the group said Collins “abandoned” women when she voted last year to confirm Kavanaugh.

Emily’s List and NARAL, both abortion rights campaign groups, have also endorsed Gideon.

Gideon faces three Democrats in the Maine primary, which will be held in June.