Why do Democrats win when the margin of victory is small? Coincidence or election theft?

Dan McLaughlin analyzed the data:

I took a look at all the statewide Senate and governor’s races from 1998 through 2013 (thanks to Sean Trende of RealClearPolitics for a big assist with the data) as well as all the statewide results in the presidential elections during that period. Let’s begin with the very closest races, those decided by less than one percentage point. There have been 27 such races since 1998, and Democrats have won 20 out of 27:

 

The odds of this happening are about 1 in 300.  This is why voter fraud is such a big deal.  It's almost impossible to detect unless someone is actually caught in the act.  Ballot stuffing, voting multiple times, absentee ballot theft,  voting for dead or people who have moved, all need to be taken seriously.  Otherwise, faith in elections will be lost and who rules will be decided by mobs in the streets.  Voter ID requirements are only a good first step.

Glenn Reynolds makes the point that 

Remember, you don’t just have to beat them. You have to beat them beyond the margin of fraud.