Leave it to the self-proclaimed Greatest President Ever — that would be your president, Donald Trump — to come up with the best rationale for impeachment, ever.

Challenged by the constitutional standard of “treason, bribery, or other high crimes and misdemeanors,” our leader has stumbled into a single set of actions that seems to meet all three.

The latest news:Pelosi announces Trump impeachment inquiry, saying ‘no one is above the law’

As America struggles with the specter that Trump has really blown it this time, it’s time for a thought no one is yet expressing.

How soon it’ll be needed

Specifically, that Democrats need to get busy, sooner rather than later, with a low-key, unified presidential transition that prepares to undo Trump’s mess. At this point, it’s hard to know how soon it will be needed.

As Republican presidential contender Bill Weld said Monday night, it’s basically impossible not to conclude that the allegations against Trump are impeachable offenses, assuming they are backed up by a whistleblower complaint and findings by the intelligence community’s inspector general that the administration is doing its best to suppress.

Also read: Why Trump impeachment threat is now rattling stock-market investors

But in case you’re especially hard to convince, let’s review what we think we know.

Trump ordered aides to impound about $400 million in military aid to Ukraine, which has for five years been fighting to protect itself and its democracy from Russian proxy-military incursion. He then pressed Ukraine’s newly elected president, Volodymyr Zelensky, to reopen an investigation of a Ukrainian natural-gas company that had been closed, without charges, hoping to find dirt — not on the strongman but on Hunter Biden, an outside director of the company whose father, Joe, is running to replace Trump next year.

Collusion with campaign

And he wanted Zelensky to coordinate that probe — not with the State Department but with Trump’s personal attorney and fixer, Rudy Giuliani. According to the Wall Street Journal, Trump asked eight times about the probe — again, Trump envisioned a fraudulent one, since Ukrainian officials had already closed the case.

Now he’s selling a Santa Claus story that he was fighting Ukraine’s corruption — as he fought corruption in Russia, where he’s best buds with Vladimir Putin’s kleptocracy. And in Puerto Rico, where a three-person company from the hometown of Trump’s then–interior secretary won a no-bid contract, later rescinded, to rebuild Puerto Rico’s electrical grid after a hurricane.

And in his own cabinet, which has included Wilbur Ross at the Commerce Department, Tom Price at Health and Human Services, Alex Acosta as labor secretary, Scott Pruitt at the Environmental Protection Agency, Ryan Zinke at the Interior Department and so on. And on his lawn, where Republican Chris Collins managed to get photographed in the very act of criminal insider trading, according to an indictment.

Triple play

Let’s be real. If Trump tied military aid to Ukrainian interference in our election, that’s extortion, or solicitation of a bribe. If he asked Ukraine to help his campaign out of the goodness of its heart, as he has seemed to confirm, that’s a crime called conspiracy against the United States — not the criminal-law definition of treason but within dictionary definitions. (It’s also a campaign-finance violation.)

And the assertion of false privileges to keep the whistleblower’s complaint from Congress covers “other high crimes and misdemeanors.”

Triple play — no president has ever done that before.

The transition

Now, about the transition.

About three weeks ago, I called Chris Lu, who ran Barack Obama’s transition in 2008-2009, to ask whether Democrats should set up a unified transition effort this year in anticipation of next year’s election.

The idea was twofold: to send a message that mostly unified Democrats agreed on the need to undo Trump’s policies and to get moving quickly on reversing them.

It’s especially necessary in areas such as trade and climate, where Trump’s policies have done tangible damage. (Bank of America Merrill Lynch estimated last year that Trump’s trade tweets alone took 6% off the S&P 500 SPX, +1.59% . ) The idea is to be ready to do, on Day 1, all the things Democrats are promising to do right away.

Lu was skeptical. He thought there was time to get going next year on the early executive orders needed to undo Trump’s border policies, tariffs and to withdraw the government’s court defenses of a whole list of Trump’s disputed environmental-policy changes.

After all, Lu said, it’s simple to file a notice with a judge that a Democratic president won’t try to kill Obama-era methane-emission rules anymore, or will withdraw rules the EPA proposes to replace them, for example.

Pence exposed as well

But now it’s looking likelier that Trump may fall.

And since Vice President Mike Pence apparently got himself involved in the scheme, meeting with Zelensky when Trump skipped a summit to monitor the path of the most recent hurricane from his golf course, he’s got significant legal exposure, too.

So it may be time to get cracking on transition, after all.

You never know when the dam will break. It’s cracking now.

If Pence falls, it would set up the ultimate misbegotten Trump troll — in the end, the joke’s always on him. Unable to nominate a vice president who can be confirmed by a Democratic House, he’d face a Senate judging him in the harsh light of senators’ own re-election prospects.

And waiting at the end — of the trial and of a decade of Trump’s snidely sexist tweets about her — would be President Nancy Pelosi.

Lowers voice, speaks rapidly ... Hail to the chief.

Tim Mullaney is a MarketWatch columnist.