The American Civil Liberties Union is the latest group to apply pressure on Republican Sen. Susan Collins, joining another group, Demand Justice, that wants her to oppose any Supreme Court nominee who declines to express support for legal abortions.

The ACLU’s $150,000 campaign that began Friday featured an ad praising Collins as an “independent voice” for Maine who stood up to efforts to eliminate funding Planned Parenthood funding. It said Americans need to know that the nominee will support the Roe v. Wade decision that legalized abortion.

Demand Justice also has started airing ads in Maine and Alaska, home to Republican Sen. Lisa Murkowski, part of $5 million it plans to spend to pressure senators.

That’s on top of regular people weighing in. Some have been sending coat hangers, which symbolize dangerous abortions women used to undergo before the procedure was legalized.

On Wednesday, Collins heard from both sides when he marched in her local Fourth of July parade in Bangor.

“I can only do what I think is right,” she said.

Collins has said she’d oppose any nominee who was hostile to legal precedents. She said a nominee who’d seek to overturn that decision “would indicate an activist agenda that I don’t want to see.”

But liberal groups including the ACLU say senators who back abortion rights can’t settle for statements that the nominee will respect legal precedent.