Complex sentence: Proctor ran for reelection in 1946 but lost the Republican Primary to Ernest W. Gibson, the first Governor of Vermont to be denied renomination.
Split into simpler sentences: Proctor ran for reelection in 1946 but lost the Republican Primary to Ernest W. Gibson. Failing to get nomination for re-election in 1946 Proctor was the first Republican Governor of Vermont to be denied renomination.