BOSTON – It looks like the Boston Teachers Union has purchased itself a pet mayor, after all.

There’s nothing unusual about that. The unions have always funded Democratic candidates for all sorts of offices for years, and in turn expect those candidates to do their bidding when they’re elected.

But BTU leaders never had the courage to admit they spent almost half a million dollars to put their candidate for mayor of Boston over the top in the waning days of the fall campaign.

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In fact the union president flatly denied it.

But now it’s been confirmed that the American Federation of Teachers, the BTU’s parent organization, was the sole donor of $480,000 used by a political action committee for a last-minute ad campaign on behalf of Martin Walsh, the union-endorsed mayoral candidate, according to a report from LegalProNews.

The ad blitz was widely credited with helping Walsh pull out a close victory in November over his opponent, John Connolly, who was highly critical of the union during the campaign.

Walsh has denied any knowledge of where the money came from. Any coordination between his campaign and the PAC might have violated campaign laws.

When asked by the Boston Herald three weeks ago whether AFT and BTU had any connection to One Boston, the PAC that purchased the ads, BTU President Richard Stutman said “absolutely not,” the news report said.

As it turns out, the money was funneled from the AFT to a group called One New Jersey, which sent it on to One Boston, according to Joshua Henne, a spokesman for One New Jersey.

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While there was apparently nothing illegal about the ad campaign, which was considered an independent expenditure by a group not tied to the Walsh campaign, some fault the teachers union for not taking full credit much sooner.

“As a Boston public school parent, it really bothers me that our teachers union wouldn’t have the respect for all of our parents and children to put their name behind a $500,000 contribution,” Connolly was quoted as saying. “I have the deepest respect for our teachers – but I don’t have that same feeling for the leadership in a union that wouldn’t put their name behind such a large contribution. And the AFT and the BTU are one and the same.”