After the March 6 primary election, Tomball and Magnolia residents may cast a ballot for runoff races. A runoff election occurs when no candidate in a primary race receives more than 50 percent of the vote. The two candidates receiving the largest percentage of the vote advance to a runoff election May 22 to determine who will take part in the Nov. 6 election. Republican candidates Charlie Riley and Greg Parker will face each other in a runoff for Montgomery County Precinct 2 commissioner. In the race for U.S. District 10, Democratic candidate Tawana Walter-Cadien joins contender Mike Siegel in a runoff election. Depending on place of residence and party, additional candidates may appear on the May 22 ballot. While the voter registration deadline has passed for the May 22 election, early voting for the primary runoff election runs May 14-18. Residents who did not vote in the March 6 primary election can still vote in the May 22 primary runoff election. However, residents who voted in the March 6 primary election must vote with the same party in the runoff election.