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.
He attempted to retain office in 1908 and secured renomination from his party's local meeting. Nonetheless, he was defeated by Republican Nathan E. Kendall in the general election, which saw Republicans triumph in all major contests across Iowa.