Sen. Kirsten Gillibrand on Tuesday pledged to stop accepting campaign contributions from corporate PACs, joining a small group of sitting Senators who made a similar move.

The backdrop: The pledge by the New York senator, who’s up for re-election, coincides with an endorsement from End Citizens United, a Democratic group created in response to the U.S. Supreme Court’s landmark ruling in 2010 that allows unlimited corporate spending to support political campaigns.

Gillibrand's announcement on Twitter: