Say this for the dim bulbs of the GOP: They finally made a decision. It is now Marco Rubio or bust.

While spending months burning through mountains of money for next-to-nothing results, party leaders, candidates and their backers took comfort in the theory that Donald Trump was winning only because the Republican field was so large. With Rubio now designated the favorite son of the anti-Trump crowd, the theory will be tested Tuesday.

If Trump runs the table or anything close, it’s game over. Not just for Rubio, but also for the party’s entire establishment. Trump is a total disrupter, and the GOP would never be the same.

The slashing of the long knives that Rubio started last week will continue until the polls close. The baby-faced senator from Florida is on a feverish pace of interviews, rallies and attacks because he has nothing to lose and no time to waste.

The vitriol is a sharp departure from Rubio’s optimistic demeanor, but in keeping with a campaign that has been historically weird. The starting assumption was that a talented field — 16 candidates at one point — would sort itself out to where three or four survivors would compete for Tuesday’s nearly 600 delegates.

Nothing went as planned, yet long after Trump stole the spotlight, his opponents and critics continue to misread the mood of actual voters. The people who gave the party John McCain and Mitt Romney still don’t seem to understand what is hitting them. Their biggest mistake is that their contempt for Trump sounds like contempt for his voters.

Recall that just before the Iowa caucus, the conventional wisdom insisted that Trump’s supporters wouldn’t show up. When he underperformed there, they said all would soon return to normal.

But a funny thing happened on the way to normal. Trump won the next three states, and his victory margin grew, along with his delegate count. He became such a force that even unaffiliated GOP leaders found themselves boxed in.

They were certain they would lose the election with Trump as the nominee, and increasingly fearful they would lose without him. Now they are uniting behind Rubio to make their last stand.

I don’t underestimate the freshman Cuban-American’s political talent, or the enthusiasm generated by the crush of time. But I can’t shake the feeling that Trump, for all his obvious flaws, is tapping more deeply into the American DNA.

The bombastic New Yorker’s appeal is not about issues, which is why he gets away with providing only declaratory pronouncements. Nor has he built a coalition by making pork-barrel promises and genuflecting before interest groups.

Rather, Trump’s appeal is about the state of the nation and the world, and the sense that America isn’t just off course, it’s about to go over the cliff.

To his supporters, Trump is the one person who gets that — and is capable of stopping it. Rubio can punch holes in Trump’ s record, but I’m not sure he can move many voters.

In a thoughtful letter, reader Edward Sukenick offers a pointed view of the Trump phenomenon. He writes: “Obama has diminished the pride Americans have in the greatness of our country. His apparent conviction that we are not an exceptional country is robbing us of the essence of who we are. Through Trump, people are out to do to Obama what his policies have done to the country — shove it down his throat.”

Trump, of course, is not running against Obama, but the letter reflects a truth of politics: Each president is a reaction to the previous one. When the country sees the incumbent as a failure, the pendulum swings hard in the opposite direction.

That’s how we got Obama, the ultimate anti-George W. Bush. And with the nation polarized and the world in chaos, the pendulum is swinging far again; in every conceivable way, Trump is the ultimate anti-Obama.

That is why, despite the organized opposition and his own limitations, I believe Trump will win the nomination. And he will do it the old-fashioned way: He’ll get the most votes.

Another pig at the Blasio trough

If you’re looking for a metaphor of the de Blasio administration, look no further than the scandal involving the head of the police Civilian Complaint Review Board. It features an anti-cop prejudice with an insider’s cozy relationship with taxpayer cash.

Lawyer Richard Emery sealed his fate by saying police unions complaining about him were “squealing like a stuck pig.” The unions wanted his removal because Emery’s law firm sues the NYPD and individual cops on behalf of New Yorkers claiming abuse. One report said the firm got more than $1 million of settlements just since he was appointed by Mayor Putz in 2014.

The city’s Conflicts of Interest Board approved Emery’s dual roles, with minor restrictions, proving the board is a rubber stamp for anything the mayor wants. There is no way in the world Emery should be heading the CCRB while having a financial interest in suing cops.

Tellingly, Mayor Bill de Blasio was silent over the smear until Gov. Andrew Cuomo demanded that Emery apologize or resign. The resulting “sorry” was half-hearted, but even a genuine apology wouldn’t resolve the glaring conflicts.

Sadly, it fits a pattern. The mayor is establishing a rancid pay-to-play culture, with his friends and allies often getting favored treatment. Showing Emery the door wouldn’t fix that, but would signal that de Blasio realizes he’s mayor, not king.

Flipping the script on Hillary

Stop the presses: The New York Times editorial page has delivered a blistering demand for Hillary Clinton to release the transcripts of her paid speeches to Goldman Sachs and other bank groups.

“ ‘Everybody does it,’ is an excuse expected from a mischievous child, not a presidential candidate,” the editorial began.

It accused her of giving four different answers about why she won’t release 51 speeches, for which she was paid $11 million. The paper said, “Voters have every right to know,” and said her refusal “fuels speculation about why she’s stonewalling.”

My only quibble is that the Times said her refusal “plays into the hands of those who say she’s not trustworthy and makes her own rules.”

In fact, her decision to take the money in the first place proves without a doubt she’s not trustworthy and thinks she’s above the rules.

No respecting this authority

Little heads roll. A Port Authority operations manager at Kennedy Airport was arrested for taking a free flight to Miami, a hotel room and meals from a cargo handler. By accepting the $3,000 gift, Sean Porter “chose to enrich himself and tarnish the reputation of the agency,” the inspector general charged.

OK, it was wrong, but no $3,000 freebie can “tarnish the reputation” of the Port Authority. This is an agency that in 2004 promised a new transit hub in five years, at a cost of $2.2 billion.

Instead, it delivered Santiago Calatrava’s winged monstrosity, which opens this week at a cost of $4 billion. And nobody got arrested.