Republican establishment frontrunner Marco Rubio picked up a major new donor who happens to be one of the most important money-men bankrolling Democratic Chicago mayor Rahm Emanuel.

Chicago-based hedge fund honcho Ken Griffin has joined Team Marco, and has chipped in “several million dollars” to the pro-Rubio super-PAC, Rubio’s campaign confirmed Wednesday.

Griffin was Emanuel’s #1 source of cash during his 2015 mayoral re-election campaign, when Emanuel fended off massive last-minute black opposition caused by his closing of many predominately black public schools.

In fact, Griffin proved to be Emanuel’s ace in the hole. When Emanuel came up short of a ballot-box majority in the primary and was forced into a run-off against a feisty opponent, it was Griffin who kicked in $950,000 in emergency donations to the pro-Rahm campaign groups.

Emanuel is now facing a veritable popular uprising against his mayoralty in Chicago, with protesters lining the streets Wednesday night demanding his resignation over his handling of the Laquan McDonald police shooting case.

National Democrats Hillary Clinton and Barack Obama are sticking with Rahm, the former Obama White House chief of staff, but the black community continues to agitate and call for redress of grievances.