Republicans don't do well when voter turnout is high, and voter turnout is always highest in Presidential election years.

The Republicans are terrified about running against Hillary because women will turn out in droves for the chance to vote for the first female President, and there will likely be a coattails effect that will trickle down to the Senate and House races. Carson will get votes from older more conservative women, but Hillary will get the lion's share of votes from younger women (especially first time voters) who think that they, not politicians, should control their reproductive decisions.

Look for Republicans to pull out every dirty trick imaginable to hurt Hillary next year. It'll make it all the sweeter when she kicks their azzes!!