While there may or may not be "lots of convictions" for this very thing (still to see any evidence), the case you provided as an example did not culminate in "a conviction". There was a "judgement" enter in this civil case that resulted in ordering a new primary for the Democratic party nomination for mayor.
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Even with the redo, the result was the same. But then a cursory glance at Bridgeport municipal politics would elicit a 'WTF' regardless of whatever outcome. It's obviously a Dem's town and within the party it's an eat your young game.
Some interesting quotes from a local report on the later mayoral election(s),
A new election between Bridgeport Mayor Joe Ganim and his Democratic opponent John Gomes was scheduled for Jan. 23 after a state Superior Court judge concluded that last year’s primary between the two men was marred by widespread ballot fraud.
www.ctpublic.org
And still mayor.