| Normally when more than one candidate from the same party files for an office, the political party committee for that district chooses between a primary, convention, or caucus. Virginia has a rather peculiar law which allows incumbents facing a same-party challenger to choose a nominating method.
This is, on its face, insane. Republican Delegate Lee Ware has pre-filed a bill to repeal this incumbency bonus, but it remains to be seen whether 140 incumbents want to vote away their best weapon against upstart intra-party challenges.
Invariably the incumbent--who typically has better name recognition--will choose a primary, and win. Very rarely do incumbents in this state find themselves overthrown in a primary (Delegates Bob Hull from 2009 and Gary Reese from 2005 come to mind, but they are exceptions).
Both parties have areas of the state with heavy one-sided party alignment, but eliminating the incumbent advantage in nomination contests is more important for Democrats, who have a stranglehold on majority-black districts that often reach up to 70-90% Democratic performance. Senators and Delegates who are elected in single-party areas of the state are practically guaranteed their seat until they give it up, and can choose whatever method of nomination they believe will be most advantageous to them.
Of course, this doesn't eliminate any pro-incumbent bias in the political party committees that would make this selection--but that's the party's problem. I hope that Virginia's legislators have the courage to eliminate the statutory incumbent protection.