Bloomberg testified Monday. He said he never would have donated more than $1 million to the state Independence Party in 2009 if he had thought it wouldn't be used on a poll-monitoring operation.
Prosecutors say former aide John Haggerty convinced the mayor and his staff to pay for a $1.1 million poll-monitoring operation that never materialized. They say he instead used most of the money to buy a house.
The billionaire mayor says he's unhappy about the loss. He says a lot of good could have been done with $1.1 million, and he called it "a lot of money."
John Haggerty denies the charges.
Prosecutors do not accuse the mayor of any wrongdoing, and Bloomberg's representatives have said his campaign broke no laws and followed standard practices.
Defense lawyers used their opening statements to flatly accuse him of "campaign fraud." Bloomberg's spokesman says the tactics are a sign of desperation.
Haggerty, 42, is a veteran of several prominent New York Republican campaigns. As a volunteer on the 2009 campaign of the Democrat-turned-Republican-turned-unaffiliated mayor, Haggerty was the point man on "ballot security," a term used mainly by Republicans for poll watching with an eye to preventing voter fraud.
He presented Bloomberg campaign aides with a $1.1 million budget that included more than 1,300 paid poll watchers, an office, two-way radios and other expenses, according to prosecution filings and documents aired at the trial. Prosecutors say Haggerty did little of what he promised and used about $750,000 of the money to buy his brother's share of their late father's home.
Bloomberg financed the plan with a personal donation to the Independence Party that didn't have to be reported until after the election. Haggerty's lawyers argue that Bloomberg was trying to distance himself from a practice that has at times been subjected to court scrutiny as an alleged tool for voter suppression, something that Bloomberg's aides deny.
Since the mayor's donation to the party could not legally be earmarked for a specific purpose, it is not evidence that any money was stolen from Bloomberg, the defense argues.
The trial has offered an unusual peek behind the scenes of the mayor's self-financed campaigns and inside City Hall, as some of his closest aides have answered questions about their relationship with the mayor and how they spend his money. Former Deputy Mayor Kevin Sheekey said on the stand that he didn't enjoy his first two years in office.