Donald Trump Attends Costume Party with Superwoman/Kellyanne Conway

Kellyanne Conway lifted Donald Trump all the way to the White House, but there's one thing even Superwoman couldn't do -- get the Prez elect into a costume.

Trump's campaign manager slipped into a tight and leggy Super outfit herself for a "Heroes and Villains" bash thrown at Robert and Diana Mercer's family estate on Long Island Saturday night ... which Trump attended too.

Tight as the Prez elect is with Conway and the Mercers -- their daughter Rebekah's on his transition team -- he wasn't down for playing dress up at the annual event for the super-rich.

Other guests in costume included a Tonya Harding, a Cruella Deville and at least 3 Ruth Bader Ginsburgs ... according to Bloomberg.

Not a single Kryptonite-colored Hillary costume though. That would've killed.