When a Republican is replaced by a Democrat do to infighting between the Tea Party and mainstream Republicans
In 2012 in Indiana Republican Senator Richard Lugar was a popular incumbant who would have been easily re-elected, but he was defeated in the Republican primary by Tea Party candidate Richard Mourdock, so then in a Tea Party turnover the Senate seat went to Democrat Joe Donnelly.
A strategy in which Republicans are trying to prevent people who might oppose them from voting, typically the poor, elderly and minorities. Usually they will claim they are just trying to stop voter fraud even though there is no evidence that that has been a problem
In Texas as part of their Voter Suppression program a concealled carry permit can be used as an ID to vote, but a student ID from one of their state colleges does not count, it's pretty obvious who they're trying to stop from voting.