Last night, if you walked into almost any bar in the vast reaches of Brooklyn, all the big screen TV’s were tuned to one event. 

Yes, the trendy, young patrons everywhere across the city demanded the barkeeps switch channels right away…they did not want to miss a second of the action! 

Was it the NHL Islanders playoff game? An early baseball matchup? NBA Hoops? 

No! Brooklyn bar owners were scrambling to meet the demands of pushy hipsters desperate to watch Thursday’s Democratic debate in their home borough.

Some bars went all in, decorating with American flags and, (heavens above!) ditched plans to show the Islanders playoff game against the Panthers, in favor of the showdown between Hillary Clinton and Bernie Sanders at the Brooklyn Navy Yard.

Why!?!?!

As one bar owner noted: “Any reason to have a party at the bar is a good reason.”

Some bars know they’d better show the debate — or else.

“The liberals get a rather vicious here,” said Ryan Khal, who owns Park Slope’s Pacific Island, where about 125 people crowded into two rooms to watch the Navy Yard faceoff.

Sports bars even shifted! In Flatbush, the 773 Lounge is converted itself from a Rangers Sports bar to a political pub — at least for a night. “A bunch of young political people approached me … they’re very Bernie-centric,” owner Billy Caine said. “We’re one of the few bars in the area with big TVs.

Caine plans to show the Islanders playoff game on a few of his 14 flat-screen TVs — with the sound off. The debate will be hooked up to the entire sound system.

Park Slope’s KBH beer hall is expecting 200 people on a Thursday evening — a mix of Islanders fans and political junkies.

“A lot of people don’t have cable or the room to have people over. We like this to be their extended living room,” said manager Marquis Williams.

Williams couldn’t forgo showing the Islanders game entirely, since the Barclays Center — the Islanders’ home turf — is down the street.

“We’ll be balancing the two,” he said.

Who will win? Bernie? Hillary? The Islanders?

It doesn’t matter. In the end the winner will be the fans.