In a rare, intraparty slap, Buffalo's Mark Schroeder says he's offended that Espada is a perceived leader.
"He's a thug," Schroeder says.
Schroeder has no power to force a vote in the Senate.
Espada made a Senate coup possible in June by siding with Republicans, who gave him a top leadership post. A month later, he returned to the Democrats to restore their majority, in exchange for another leadership post. Soon after, Espada's son was hired then withdrew from a high-paying Senate job.
Espada also is being investigated for state grants directed to his health clinic.
There was no immediate comment from Espada.