Sen. Claire McCaskill, D-Mo., will filibuster Neil Gorsuch, she announced today on Medium:

This is a really difficult decision for me. I am not comfortable with either choice. While I have come to the conclusion that I can’t support Neil Gorsuch for the Supreme Court — and will vote no on the procedural vote and his confirmation — I remain very worried about our polarized politics and what the future will bring, since I’m certain we will have a Senate rule change that will usher in more extreme judges in the future.