Enter stage left

Actor Cynthia Nixon, channeling Bernie Sanders and her close ally Bill de Blasio, is leaping into the political fray to challenge the man she portrays as big, bad, barely liberal Andrew Cuomo in New York’s Democratic gubernatorial primary. Competition is healthy; coronations are for monarchies, not democracies. And Cuomo can be a real piece of work. But let’s not get carried away.

Nixon’s campaign launch script savages Cuomo for “choices usually made by Republicans,” including “starving the state and its cities of the most basic services” through “inhumane” budgets “passed on the backs of our children, our working and middle class, and our elderly.”

Funny; somehow, the state budget has managed to grow to $164 billion, from $135 billion eight years ago. Somehow New York’s schools spend more per pupil than any other state’s.

Yes, the state’s budget has risen more modestly than the city’s thanks to a Cuomo property-tax cap and relative fiscal discipline, but the end of runaway Albany spending is cause for praise.

And how exactly is a governor who passed the nation’s toughest gun laws, championed gay marriage, zeroed out state university tuition for most families and hiked the minimum wage a scrooge?

We wish Nixon luck focusing attention on what she calls “New York’s corrupt political establishment”; Albany, no thanks to Cuomo, has sidestepped strong ethics reform far too long.

And we cheer her focus on Cuomo’s biggest management failure, crumbling subways — though note that she’s running interference for de Blasio as he refuses to put up $400 million in urgently needed cash for a subway rescue plan.

At a time when a certain famous person, having promised to bring fresh air to Washington, has polluted the capital with equal parts ignorance, confusion and corruption, New Yorkers ought to be wary of a broad-brush celebrity candidacy.

Nixon boasts of riding the subways daily. Far more important, she must prove she can navigate complicated policy underground and above it.