Low turnout is a problem nationwide, but it's particularly acute in states that use runoffs. It's compounded further when there are runoffs in primaries, where participation is already. An instant runoff (RCV/IRV) could help improve this:

Voter participation is always lousy in primaries. Even when we have statewide contests in both parties, it’s extraordinary to see 20% of registered voters participating, so candidates often win their nominations with the votes of as few as 5% of the state’s registered voters.

In races that go to a runoff, even those stalwarts who participate in primaries lose interest, as turnout tends to drop off by as much as 40%.

This would be worrisome enough if all or even most elections were still decided in the November general election, as most voters apparently believe they are. Although the Charleston County sheriff’s race will be, nearly all S.C. legislative and congressional races, as well as a lot of county-level races, were decided either Tuesday or two weeks before that.

We haven’t figured out how to persuade more voters to participate in the first round of primary voting; we’ll just keep urging them to do that and hope that eventually it does some good. But there’s a simple and effective way to ensure that more voters decide who wins runoffs — a way that South Carolinians in the military or living overseas already use.

It’s alternately called instant-runoff or ranked-choice voting, and it’s a lot more complicated to explain than it is to actually do: When you cast your primary ballot, you have the option of also selecting your second choice — and even ranking all the names on the ballot if you’d like. If your first-choice candidate finishes in last place, then your second-choice vote gets allocated to that candidate. If your second choice finishes last in this recalculation, your third-place vote would be allocated in a third round of tabulations. It’s as if you went back out and voted in the runoff, except you don’t have to take the time to do that, you don’t have to pay for election officials to hold a second round of voting, and nobody has to live through two more weeks of campaigning.

Read more here.