Why super PACs have moved from sideshow to center stage for presidential hopefuls "....One category of 2016 contenders cannot take part in the early super PAC rush: federal officeholders, who, like official candidates, can’t coordinate with the groups. That’s one reason there are no major super PACs yet for GOP Sens. Marco Rubio of Florida, Rand Paul of Kentucky and Ted Cruz of Texas, all of whom are considering presidential bids."....