Republicans need to win just one of three special elections Tuesday to re-gain a veto-proof majority in the Missouri House.
Voters in Tuesday's primaries will be picking party nominees for the November elections. But in three areas, they also will be electing replacements for vacant House seats.
Special elections are occurring in the 67th District in St. Louis County, the 120th District in east-central Missouri and the 151st District in southeast Missouri.
The winners likely will take office by the Sept. 10 veto session. That means they could provide pivotal votes when lawmakers consider whether to override Democratic Gov. Jay Nixon's vetoes of budget items, tax breaks, abortion restrictions and other bills.
Republicans currently hold a 108-51 House majority over Democrats. It takes 109 House votes to override a veto.