EXCLUSIVE

No one makes it rain like sexually repressed old white men -- at least according to a manager at a strip club in Tampa, who tells TMZ the club's business has DOUBLED ever since the Republican National Convention rolled into town.

The manager at Skin Tampa tells us, the club has been sending its hottest girls to the RNC with cards and flyers -- offering free entry to anyone attending the convention -- and the response has been insane.

The manager says the club's traffic has exploded thanks to the special RNC deal -- and revenue has doubled with it.

But the club isn't stopping there -- according to the manager, it's going the extra mile to welcome everyone at the RNC, decking the place out with Republican-themed decorations.