An opportunistic lawmaker hopes to use a controversial ruling that would knock 20 stories off of a nearly-complete Upper West Side condo highrise to cut another building in Midtown down to size.

“We’re going to file a motion to [re]argue based on this,” said Councilman Ben Kallos (D-Manhattan), who represents a swath of Midtown and the Upper East Side.

The lawmaker’s target is an 847-foot pencil-thin skyscraper currently under construction at 430 East 58th Street that he would like to see cut down to just 400 feet.