Super PACs and other independent groups spent almost $1 million in Kentucky and Arkansas, the two states that held primaries on Tuesday. 

So far this year, super PACs have spent at least $16 million on congressional races, a fraction of what they've pumped into the presidential campaign. But the smaller amounts spent in congressional races have sometimes produced big results, pushing a few candidates to primary victories. So far, super PACs and other independent group have spent on 88 races.

In Kentucky the big spender was the Liberty for All super PAC,which run by a few twenty-something supporters ...