Picture a man falling down a flight of stairs backwards, his arms flailing as he tumbles towards his doom.

That's Gov. Chris Christie today. Any scrap of credibility that survived his craven embrace of Donald Trump has been incinerated in the Bridgegate trial.

Five witnesses - including three who remain steadfast allies - refuted his claim that he was "blindsided" and knew nothing about his staff's involvement in the lane closures before the rest of us did.

Among those who contradicted the governor under oath are Michael DuHaime, his chief strategist for the last decade; Mike Drewniak, his press secretary during that entire stretch, and Deborah Gramiccioni, his deputy chief of staff at the time. You can read excerpts from their testimony here.

The governor is not charged. Prosecutors say that he knew about the lane closures as they occurred, but knowledge of the plot is not a crime in itself. And no one in this trial has suggested that Christie ordered the lane closures.

But the rules of the courtroom are one thing, and the rules of politics are quite another. It's tough to govern after absorbing a blow like this.

"It's been incredibly damaging to hear one person after another directly contradict him," says Julian Zelizer, a professor at Princeton University. "And if the national election goes as poorly for him as some think, that will add to the damage. Because he is forever connected to Donald Trump."

In his famous mea culpa press conference in January of 2014 that ran about two hours, Christie left himself no wiggle room:

"I had no knowledge of this -- of the planning, the execution, or anything about it," he said. "I would never have come out here four or five weeks ago and made a joke about these lane closures if I had an inkling that anyone on my staff would have been so stupid but to be involved."

But he did know. The five witnesses reported conversations that took place between September and December of 2013, and each included discussions of his staff's involvement in the lane closures.

The most toxic account came from David Wildstein, the author of this stunt, who swore that he and Bill Baroni, a defendant, told the governor at the time the lanes were closed -- and described it as an act of political revenge. The most benign account came from the governor's allies who told him of Wildstein's claim that Bridget Anne Kelly, the deputy chief of staff, was involved.

So let's stick to the benign version. Did he respond by calling in Kelly to ask what she knew?

No. Her office was across the hall from his, and he passed through it once or twice a day on the way to his own office from the back door of the capitol that he used routinely. But everyone agrees he never stopped to ask her about it.

Instead, he tried to bury it. He lied to the public when he said he was blindsided. He mocked Democratic legislators who opened the inquiry as partisan hacks. And he hired the law firm of a woman he once described as a "dear friend" to conduct an "independent" investigation that somehow missed all of his fingerprints.

The cost to the taxpayer: More than $10 million.

* * *

What now?

Christie has 15 months left in his term, and he's unlikely to be impeached or to resign. Which means New Jersey is likely to limp along for now, as its many problems fester.

Yes, folks, things can get worse.

The Legislature can impeach a governor for any reason it chooses, even for eating a ham sandwich, and its verdict can't be challenged in court. But even Democrats say the nuclear option is probably overboard, given that federal prosecutors found no proof that the governor committed a crime.

Removing Christie from office after an impeachment would require 27 votes in the Senate, which means at least three Republicans would have to jump off their cozy home on the governor's lap long enough to sink in the knife. Not likely.

And practical concerns intrude. An impeachment and trial takes time, and might clip only a few months off his term. It would also elevate Lt. Gov. Kim Guadagno, giving her a boost against a Democrat in 2017.

What about pressing Christie to resign? It's a wonderful dream, but it's not in his genes. He has no shame.

We could gather torches, march on Trenton, and haul him away hanging from a rail. But I checked the state Constitution, and it makes no provision for that.

Sen. Loretta Weinberg, one of the heroes of this story, is particularly furious about the $10 million wasted on the white wash. She wants that money back.

But I asked her what legal basis she would have to do so. The firm, after all, was hired to protect Christie and fulfilled its part of the bargain with shameless efficiency.

"I still have people doing legal research into that," she said.

* * *

Bridgegate is Christie's white whale, the beast that keeps coming back to take another bite. It was a key reason he lost his campaign for president, and it began his descent in New Jersey. He has paid a steep price.

Still, it drives me nuts that he's never been forced to answer questions on this, under oath, and in public.

The Legislature could make that happen. And this trial has provided a road map. Bring on the five witnesses who contradicted the governor, and then bring him in.

"All the surrounding characters are clearly pointing at him in a way that make it hard not to conclude anything but that he had a hand in this," says Assemblyman John Wisniewski (D-Middlesex).

I asked the two Democratic leaders about that -- Assembly Speaker Vincent Prieto (D-Hudson) and Senate President Steve Sweeney (D-Gloucester) -- and both hedged.

What are they afraid of? What is complicated about this one? Neither man would answer that question, which is unnerving, given that their approval is the needed first step.

Wisniewski and Weinberg were co-chairs of the investigative committee that broke this scandal wide open. They suspended operations to make way for the criminal trial, and both want to resume their work. But they haven't been able to get an answer either.

"They always seem uncomfortable when we talk about subpoena power," Weinberg says.

Hmm. That's a cryptic comment. But it is true that Weinberg and Wisniewski had to pull teeth the first time around to get subpoena power, something that is routine in Congress.

Could it be that the old boys in Trenton feel threatened by the idea of a subpoena landing on their own desks someday, or the desk of a friend? Is there a more innocent explanation for this reluctance to grant that power more readily? Neither wanted to discuss details until the trial is over.

I have to believe they will agree, and that the Legislature will reopen its inquiry and follow the obvious leads exposed by this criminal trial, leads that point straight to the governor.

If they don't, then Christie will no doubt leave office clinging to his story, repeating his claim that he's been "exonerated" by his own investigation, and by the decision of federal prosecutors to issue no indictment.

So let's keep those torches handy. If Democrats let Christie walk on this, we may need them.

More: Tom Moran columns

Tom Moran may be reached at tmoran@starledger.com or call (973) 836-4909. Follow him on Twitter @tomamoran. Find NJ.com Opinion on Facebook.