When the Democratic debate started Tuesday night, I was young, carefree, merry. Two hours later, when it ended, I was praying to the Almighty for a swift end to my suffering. I felt like I was 103 years old — or even older, like one of the early patriarchs in the Bible. All the life had been sucked out of my body.

This, the seventh debate in seven months, was the dullest major political event in years.

And there is no excuse for that, since there were only six candidates on stage and, therefore, a real possibility that the Democrats could ­explore their differences with one another and draw sharp divisions. After all, the first voting will take place in Iowa in only 19 days.

President Trump may have degraded our national discourse with his ­debate hijinks in 2015 and 2016, but to my surprise, I found myself longing for one of these ­exhaustingly boring Democrats to call someone else’s wife ugly or say someone else’s father had killed JFK — just to help me stay awake.

Amy Klobuchar almost jolted me to life when she had a near-disastrous moment, forgetting the name of Kansas’ governor the way 2012’s Rick Perry forgot the name of the third Cabinet department he swore he would close down. But she recovered at the end. That was lucky for her but terrible for me, as I slumped again into somnolence.

Maybe the problem is that, as the debate’s opening section on Iran revealed, most of the candidates are close to being functionally pacifistic.

They were tripping over themselves to condemn Trump’s strike on Iran’s military chief before ­declaring their intention either to pull all our troops from the Middle East or almost all of our troops from the Middle East.

Combat troops aren’t the answer, they said. They were prepared to be commander in chief because they care about health care for veterans or education for veterans, which is lovely but ­really doesn’t address the question of how they would confront threats to the United States of the sort posed by the Tehran regime.

Maybe their lack of national combativeness has infected their debating skills and made them ­unable to confront each other during this debate, because you would never really know there was a contest here one of them is going to have to win — which means the others have to lose.

The only candidate the weird politesse on the stage in Iowa Tuesday night really benefited was Joe Biden, who wasn’t especially sharp but whose entire candidacy is based on the proposition that he is the calm, wise grandfather who can restore normalcy to America.

Former South Bend, Ind., Mayor Pete Buttigieg had nothing to say. Tom Steyer had a lot to say, and trust me, you wanted him to stop saying it. Klobuchar once again seemed smart and collected . . . and the opposite of compelling.

Given how ineffective Elizabeth Warren was last night — you’ll hear she really had a great moment talking about how women win elections and men don’t, but, you know what, it really wasn’t — the only real contrast with Biden was Bernie Sanders.

Which means, quite simply, if you want passion and heat, you can go for Sanders, who once again was simple and clear and energetic and so far off the charts leftward you could almost hear the ghost of Fidel Castro whispering in his ear to cool it a little.

And if you don’t need that, or that turns you off, or that threatens you, Biden is right there to take your vote and make whatever promises you want him to make that he will stop the crazy in Washington.

Can he? Biden has some pretty crazy qualities that he has been muting, with rather more success than any of us anticipated, throughout this race. The only real question is whether he can stand up to Trump. One of the moderators asked him that question last night and he said Trump’s been going after him for a year and he’s still standing.

Oh, please.

Joe ain’t seen nothing yet.

John Podhoretz is editor of Commentary magazine.