He ran for re-election in 1908, and won renomination from his party's district convention. However, in a general election in which Republicans swept all major races on the ballot in Iowa, Hamilton was defeated by Republican Nathan E. Kendall in a close race.
Hamilton made a bid for re-election in 1908 and regained his party's nomination at its regional convention. However, he fell short against Republican Nathan E. Kendall in the general election, where Republicans dominated the polls in Iowa.