With 100 percent of precincts reporting, Knockerbocker defeated Donahue 324 votes to 187 votes, 63 percent to 37 percent.
Knickerbocker has been deputy mayor since 2010. The two candidates who are running to replace incumbent mayor Sean Murray, who did not run for re-election.
Donahue has been a fixture in the Buchanan political scene. having been mayor from 1994 to 2002 and 2008 to 2010 and also serving village trustee.
Donahue said he was proud of the campaign he ran and accused the other side of being vindictive.
"We brought all the issues to village residents," Donahue said. "They lodged personal attacks against on me and my family. That's the way they play the game. The people chose, that's their right."
Donahue ran against agreeing to another PILOT (payment in lieu of taxes) agreement with Entergy, who owns Indian Point.
"Everything will come out in the open," Donahue said. "It will hurt the taxpayer."
Donahue said this might be his farewell to public service.
"I have no regrets," Donahue said. "I stuck with the facts."
Nicolas Zachary and Richard Funchion were re-elected to the village board, fending off a challenge from Brian Smith. Zachary and Funchion had 333 and 321 votes respectively while Smith had 152 votes.
Jennifer Daly ran unopposed for village justice.
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