Prior to the March 4, Rush Limbaugh was asking Republicans in Texas and Ohio to change parties in order to vote for Hillary in the Presidential primaries. His objective seemed to be to prolong the race with Hillary and Obama.  Rush told Laura Ingraham on Feb 29:

"I want Hillary to stay in this, Laura. This is too good a soap opera. We need Barack Obama bloodied up politically, and it's obvious that the Republicans are not going to do it and don't have the stomach for it, as you probably know."

The problem is that what the voters did in Ohio was a fifth-degree felony in that state, punishable with a $2,500 fine and six to 12 months in jail. That is because in order to change party affiliation in Ohio, voters have to fill out a form swearing allegiance to that party's principles "under penalty of election falsification."
It appears that Rush encouraged Republican voters  to falsify documents  in order to rig an election.  According to The  Cleveland Plain  Dealer, "One voter scribbled the following addendum to his pledge as a new Democrat: "For one day only."