Sen. Susan Collins, R-Maine, has been drawn into a skirmish with progressive groups that she accuses of attempting to “bribe” her to vote against Supreme Court nominee Brett Kavanaugh.

The dust-up began when a campaign called Be A Hero, started last month by activist Ady Barkan, pledged to make a $1.3 million donation to Collins’ eventual 2020 opponent if the centrist GOP senator supports Kavanaugh. The effort reflects pressure that left-wing groups and abortion rights advocates are heaping on Collins ahead of Kavanaugh’s confirmation vote, likely to come in early October.