A former councillor tried to rig postal voting by collecting ballot forms from voters and getting other people to fill them in in his favour.
Muhammed Hussain, 61, from Logwood Street, Blackburn, Lancashire, admitted the election fraud on Monday. He was warned he faces a prison sentence.
The ex-Labour councillor had a 685 majority in the elections for Bastwell ward on Blackburn Council in 2002.
He was remanded on bail for sentencing at Preston Crown Court on 8 April.
The court heard an investigation discovered that 233 postal votes for Hussain were fraudulent.
An investigation began when the Conservatives, who came second in the vote, complained after more than 75% of people applied to vote by post - an unusually high number.
Hussain admitted conspiring to defraud Returning Officer Philip Watson by "dishonestly causing and permitting falsely completed postal ballot papers and accompanying declarations of identity to be submitted in the local government elections for the Bastwell ward".
The investigation revealed that Hussain had asked others to collect postal ballot forms from voters and fill them in themselves.
Mark Ainsworth, prosecuting, said: "The integrity of the electoral process must be maintained.
"In this case a number of postal votes were submitted in this local election. It is clear that Mr Hussain was deeply involved in this activity.
"He was the only person with anything directly to gain from this."
Adjourning the case for sentencing, Judge Peter Openshaw warned Hussain: "You must brace yourself for a custodial sentence."