The Senate blocked President Obama's and Democratic leaders' tax cut plans Saturday in a foreordained symbolic vote that now sends both sides back to the negotiating table to work out a viable deal. A bipartisan filibuster, led by unified Republicans and joined by four Democrats and one independent, proved there isn't enough support to back Mr. Obama's preferred option to extend income tax cuts for couples making less than $250,000 and tax increases for those making more than that. With that vote out of the way, attention turns back to the high-level working group Mr. Obama and congressional leaders set...