Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Washington (CNN) The math isn't there yet for Mitch McConnell. Within hours of the Senate majority leader unveiling a long-anticipated health care bill on Thursday, four of his Republican colleagues were quick to put a damper on things: "We are not ready to vote for this bill," the group said in a joint statement. The swift rejection may be a negotiating ploy, but the public nature of it is a reminder for McConnell of the deep reservations running through his own conference on a proposal that conservatives do not believe goes far enough to repeal Obamacare -- and the monumental challenge that lies ahead as he looks for 50 "yes" votes.Four of his Republican colleagues do not yet support the Senate health care billThe GOP majority leader needs the support of 50 out of 52 Republicans 
 Question:Many of McConnell's colleagues, however, are confident that if anyone can find 50 votes, it's their majority leader -- a political tactician who knows _ procedure inside and out.

Senate