A number of Tuesday’s primary races appear to be headed toward runoff elections in July. As such, here are some rules to mind:

NO DO-OVERS

Because the state conducts an “open” primary, voters on Tuesday were able to pick their choice of ballots regardless of any political affiliation. Not so for the runoff. As a voter, you must stick with the party ballot you choose for the main primary (in other words, you can’t cast a Democratic ballot in the main primary and then vote in a Republican runoff).

If you did not vote in the primary, you may still cast a ballot in the runoff. And you can pick the party ballot of your choice.

Open primaries are not unusual. Georgia is one of 11 states that use such a system. The others are Alabama, Arkansas, Hawaii, Michigan, Minnesota, Missouri, Montana, North Dakota, Vermont and Wisconsin.

WHY RUNOFFS

Georgia requires election winners to receive more than 50 percent of the vote — you’ll often hear politicos refer to this margin as “50 percent plus one (vote).” It can be a hard margin to reach, however, if a race has multiple candidates. If none of them break that 50-percent-plus-one barrier, then the top two finishers compete in a runoff to declare a winner. The requirement attempts to encourage candidates to reach out to more people in order to win a “majority” of their votes.

WHAT’S NEXT

Georgia’s primary runoff this year is scheduled for July 22. Winners will move on to the Nov. 4 general election.