Sen. Casey recently announced his support for the 20-week ban:
http://thetimes-tribune.com/opinion/pro-life-and-pro-planned-parenthood-1.1930507#.Vdu7d-X9YRo.twitterWith the 54 GOP Senators (even pro-choice Republicans like Pataki support a 20-week ban), the two Democrats who voted to defund PP (Manchin and Donnelly), and Casey, we have 57 votes in favor of banning abortion at 20 weeks.
The question is where the last three will come. Heitkamp is probably the next most likely. Possibilities for the final two:
Jon Tester
Harry Reid
Claire McCaskill
Mark Warner
Any others?