It's only natural that a who's-up-and-who's-down leadership struggle would consume House Republicans after the stunning primary defeat of Majority Leader Eric Cantor. There's a big hole in the party's top echelon, and it's got to be filled.But after a new majority leader is selected, and the leadership slate finished, GOP lawmakers will have to figure out what Cantor's loss means for the Republican agenda. Right now, they have no idea.That's because they don't know why Cantor lost.