Senate Minority Leader Mitch McConnell has promised to filibuster new gun control legislation, putting up a significant roadblock to Democratic efforts to move forward on the measure this week. ... McConnell is now the 15th Senator to sign on to the Republican gun control filibuster, an effort that has been spearheaded by conservative Sens. Rand Paul (R-Ky.), Ted Cruz (R-Texas), and Mike Lee (R-Utah). As the top Senate Republican, McConnell's support gives the filibuster a much higher chance of success, imperiling the already-delicate bipartisan negotiations on new gun control measures. McConnell's promise to filibuster also deflates criticism from the more...