Mayor Michael Bloomberg donated a hefty $1 million to state Senate Republicans’ general fund in the final weeks of this year’s campaign season – the single largest donation ever received by the housekeeping committee.

Senate Republicans have been the recipients of the billionaire mayor’s political philanthropy in the past. The four Republicans who were crucial to the passage of same-sex marriage received more than $10,000 from Bloomberg last year, as did local GOP senators Andrew Lanzan of Staten Island and Martin Golden of Brooklyn.

“[T]he mayor has been a supporter of the Senate Republicans for [some time] due to their support for New York City,” Bloomberg spokesman Marc LaVorgna said in an email.

The mayor also recently backed the splinter Independent Democratic Conference, which received a $75,000 donation earlier this month, according to filings with the state Board of Elections.

The donation follows a history of sustained financial support for four Democratic state Senators—Jeff Klein of the Bronx/Westchester, Diane Savino of State Island/Brooklyn, David Carlucci of Rockland County and David Valesky of the Syracuse area — who broke with their conference after they lost the majority in 2010.

“The mayor has a long history of supporting independent-minded officials who are willing to cast aside partisan politics to support New York City,” LaVorgna said.