Harry Reid explains the negotiations over a bill to curb Chinese currency manipulation that finally led Democrats to change the Senate's rules:
The bill — which is supported by business and labor interests — had garnered a bipartisan supermajority not just once but twice. With passage virtually assured, the minority reached for the only tool left to try and derail the bill, confronting us with a potentially unlimited number of votes on completely unrelated amendments. Voting on these amendments would require suspending the Senate’s rules — an obscure procedure that hadn’t been used frequently until this Congress and hasn’t been used successfully since 1941.
....We offered votes on four amendments, and they wanted five. We offered five votes, and they wanted six. Finally, we offered votes on seven amendments, including a vote on an outdated version of President Obama’s American Jobs Act, with which Republicans were seeking to score political points. Still, Republicans refused. They came back with a demand for nine votes that required suspending the Senate’s rules. The same logic that allows for nine unstoppable motions to suspend the rules could lead to consideration of 99 such motions.
I haven't heard Mitch McConnell's side of this, but this sure has the smell of truth. First, because it sounds exactly like something McConnell would do. Second, because McConnell's actions would have to have been pretty outrageous to get the notoriously milquetoast Democratic caucus to unanimously support a rules change. But I guess even a herd of cats can eventually be pushed too far.