How’s this for locker-room lore — Rep. Eric Swalwell says the real political tea ain’t spilling over cable news… it’s going down at the gym, where he claims Republicans are quietly trashing Donald Trump between sets.

We caught up with the California congressman on Capitol Hill Tuesday, and he tells us the congressional gym is where the truth really gets a workout … with GOP lawmakers privately unhappy with Trump, but way too scared to say it out loud in public in case he claps back with threats.

Now you may be thinking, “no whey that happens” — but we bench-pressed Eric a little harder, and he says it’s abs-olutely true … in fact, he compares it all to WWE, saying once the cameras are off — especially in the gym — Republicans switch personas real fast!