R. Kelly Meets with Lawyer Tom Mesereau Who Won Michael Jackson Sex Case

R. Kelly wants to change up his legal team ... by bringing on one of the most powerful, successful criminal defense lawyers in the country ... Tom Mesereau.

Sources familiar with the case tell TMZ ... Mesereau is in Chicago right now, meeting with Kelly, who is charged with various sex crimes in 4 different jurisdictions -- Illinois State, Illinois Federal, New York Federal and Minnesota State. Raed Shalabi -- one of R. Kelly's current attorneys -- accompanied Mesereau into the jail to meet with Kelly behind bars.

In case you don't know ... Mesereau has worked miracles in the courtroom. He got Michael Jackson acquitted of child molestation in 2005, and got Robert Blake acquitted of murdering his wife, also back in 2005.

We're told Mesereau has not officially signed on, but that's the plan. If he does, he will be the lead attorney and possibly the sole attorney representing Kelly.

The big question ... how's Kelly paying his legal and other bills? As you know, he's struggled to pay child support and was even jailed for a time before someone footed the bill.