Mayor Bloomberg is making good on his pledge to assist senators who support key aspects of his agenda, regardless of their political affiliation, by lending his name to a fundraiser next Monday to support Democratic Sen. Craig Johnson.

The $1,000-a-head event is being held at the Manhattan home of Michael Del Giudice, a founding member of the private equity company Rockland Capital and a former aide to ex-Govs. Mario Cuomo and Hugh Carey.

Johnson has been a fierce proponent of charter schools, which is one of Bloomberg’s pet issues. (Recall that this issue has also become a cause celebre of late for certain New York hedge funds, which are backing primary challengers like Basil Smikle, a former Bloomberg aide, against charter opponents like Sen. Bill Perkins).

Johnson isn’t the only pro-charter Democrat to benefit from Bloomberg’s assistance. The mayor has also leant a fundraising hand to Buffalo Assemblyman Sam Hoyt, who is facing a tough re-election bid this fall.

Johnson, one of just two Long Island Democrats in the Senate, has drawn the ire of Senate Minority Leader Dean Skelos and has a GOP challenger this year, (Mineola Mayor Jack Martins), but has so far managed to hold on to the seat that he won in a 2007 special election (after then-Gov. Eliot Spitzer infuriated the Republicans by tapping then-Sen. Mike Balboni to be his public safety czar).

Bloomberg has long been the Senate GOP’s largest individual donor. Interestingly, he helped Johnson’s GOP opponent int he 2007 special election, Nassau County Clerk Maureen O’Connell.

But the mayor has branched out in recent years to help certain Democrats (backing Sen. Dan Squadron in a primary against former Minority Leader Marty Connor, for example, and also supporting ex-NYC Councilman Simcha Felder’s failed primary challenge to Sen. Kevin Parker).

Deputy Mayor Howard Wolfson recently said the following about the mayor’s future endorsement/contribution plans:

“You should expect to see forthcoming announcements in the broadest possible term, but I’m not going to preview it, except to say that, as he has done in the past, he will support those candidates he believes have been supportive of New York.”

7-12-10 Craig Johnson Bloomberg Invite