Campaign officials in both parties are making efforts to run up the score in early voting in hopes of gaining an edge.

Republican National Committee (RNC) Chairman Reince Priebus is in Iowa campaigning for Joni Ernst in one of the nation’s most competitive Senate races. Priebus hit the trail on Thursday to stump with Ernst and Iowa Gov. Terry Branstad (R).

Democrats are fighting to hold the Iowa seat and are deploying First Lady Michelle Obama — one of their most popular surrogates — to campaign next month for the Democratic candidate, Rep. Bruce Braley (D-Iowa).

Michael McDonald, an associate professor at the University of Florida who runs the U.S. Elections Project, said data so far indicates that participation in early voting is likely to surpass previous midterm years.