The Libertarian candidate Douglas Butzier, who is also a pilot, was killed when the small plane he was flying crashed near Dubuque Regional Airport. Butzier, 59, worked at Mercy Medical Center - Dubuque where he was president of the medical staff and member of the Board of Trustees. He was running against U.S. Rep. Bruce Braley (Dem.) and Iowa state Senator Joni Ernst in an extremely close race to succeed the retiring long term Senator Tom Harkin. He was polling in the low single digits in the race.