Manhattan DA Cy Vance Jr. has empanelled a grand jury that is taking testimony in a case involving Mayor Bloomberg’s $750,000 contribution to the state Independence Party in 2009 that was passed on to campaign operative John Haggerty, who has never fully accounted for how he spent the cash, sources confirm.

That’s a sign the DA is moving closer to potentially bringing charges in the case, which has been open since at least February.

A Vance spokeswoman declined to comment.

The DA’s office issued subpoenas this past winter to state Independence Party Chairman Frank MacKay, Haggerty and an Albany-based lobbying firm, Capitol Public Strategies, whose address Haggerty used to register the limited liability corporation through which Bloomberg’s contribution was funneled.

Haggerty didn’t register the firm, Special Elections Operations, with the state Secretary of State’s Office until Dec. 3 – a full month after the general election.

Bloomberg cut two personal checks for $600,000 to the state Independence Party’s housekeeping account on Oct. 30 and Nov. 2 last fall. The money was to be used for party building and Election Day operations like transportation and poll watchers.

The mayor’s campaign attorney Ken Gross has referred to Special Elections Operations as a “payroll mechanism” that was set up to pay poll watchers $500 apiece.

Aides to Bloomberg have said between 200 and 300 poll watchers were hired, which leaves the bulk of the $750,000 unaccounted for.

Haggerty was recently hired by GOP gubernatorial hopeful Carl Paladino to serve as his political director, handling convention operations and petitioning.

Paladino spokesman Michael Caputo told me Paladino’s campaign is well aware of the DA’s investigation, but was “completely comfortable” and “satisfied with John’s version of events” after a long discussion with him and his attorney, former AG Dennis Vacco.