To cause someone to have doubts, worries, or concerns (about something); to introduce someone to a doubtful or worrisome idea. The candidate was doing very well in the polls six months ago, but it seems that this smear campaign has been effective in sowing a seed of doubt in the minds of voters. Recent economic turbulence in the Eurozone has sown the seed of doubt about the strength of the economy's recovery. Jim's suspicious behavior sowed a seed of doubt in Jenny's mind about his fidelity.