Wall Street had better prepare itself for the constitutional crisis that is looking more and more likely in Washington.

The financial markets this week gave us a taste of what the reaction to true chaos in the Trump administration could look like. Stocks were up sharply in the final hour of trading on Monday when all of a sudden the big gain turned into an itty-bitty one.

Someone obviously knew ahead of time that the office and home of Donald Trump’s personal lawyer, Michael Cohen, had been raided by the FBI at the behest of special counsel Robert Mueller.

Before the close of trading, the Dow Jones industrial average was up by as much as 440 points, but it ended Monday’s session with just a 46-point gain.

The drop in stock prices started before the news of the FBI raid was reported, so it’s clear that someone had the information ahead of time. But in this day and age of wild stock price fluctuations, insider trading on such news is small stuff.

So I’ll let it go, just as the Securities and Exchange Commission seems to have.

The bigger implication of the FBI raid is that someone — probably inside the government — either knows some bad stuff about Trump or is hoping (after all these months of nothing) to uncover something earthshaking.

Remember, Mueller started out probing possible collusion by the Russians in the presidential election. Mueller has said some of Trump’s people might have unwittingly had contacts with Russians, but that avenue of investigation seems like a dead end.

Then, Mueller’s attention turned to whether Trump’s people lied to investigators. That seems to still be under active investigation.

Remember, some people inside the FBI seem to have been “never Trumpers” and were still trying to foil his presidential election bid right before the 2016 vote.

Then came the effort to prove that Trump somehow colluded with the Russians to win. Mueller was appointed. Attorney General Jeff Sessions recused himself from the probe even though he would have normally been in charge of what Mueller was doing.

There has been lots of stuff since then. For example: emails from inside the FBI showing bias against Trump and indications that former FBI Director James Comey had exonerated Hillary Clinton of wrongdoing even before the FBI’s probe of her missing emails had begun. And, more recently, the firing of Deputy FBI Director Andrew McCabe just days before his leave of absence was to turn into a comfortable retirement.

The latest, of course, is the furor over the fact that Trump seems to have had affairs with at least two women while married to Melania Trump, and both were paid hush money.

Infidelity, of course, could lead to an impeachment attempt, but, as we learned in the instance of Bill Clinton, it really isn’t a crime that gets the president removed from office. But even the bigger charges, of perjury and obstruction of justice, against Bill Clinton — started by the Monica Lewinsky revelations — weren’t enough to kick him out of office in the end.

In this current mess, one thing is obvious.

The Democrats and Mueller seem to be doggedly going after Trump — a guy who was legally elected president — even if it means raiding the office of his attorney in what appears to be a clear violation of attorney-client privilege.

And the leadership of the Republican Party — Trump’s party — doesn’t seem to be coming to his defense.

If the Democrats somehow succeed in toppling the Trump administration or at the very least limiting the president’s ability to negotiate deals, make decisions on national security and do other things that presidents do, we are heading for a constitutional crisis that’s worse than we saw in the 1970s during Watergate.

Wall Street isn’t going to like that.

The quickest way to a constitutional crisis would be if Trump fires Sessions, and his new attorney general gets rid of Mueller. Or Trump could go after Mueller directly.

The current situation is worse — and certainly more complicated — than when Richard Nixon’s single- minded bandits broke into the Watergate office of the Democrats back in 1972.

There’s no doubt that was a constitutional crisis, and it led to Nixon’s resignation.

I’ll say it again. I don’t think Mueller has the goods on Trump himself. But if the Republican Party doesn’t come to Trump’s defense and the Democrats get their way, the slow-motion bloodless coup that is now being attempted will lead to disruptions.

There’s one other thing that needs investors’ attention: an upcoming report from the inspector general of the Justice Department that could make the chaos in Washington even worse.

Inspector General Michael Horowitz looked into the sketchy investigation of Hillary Clinton’s missing emails and his findings are not expected to be good news for the Democrats. It could be especially bad if two anti-Trump FBI agents named Peter Strzok and Lisa Page cooperated with the IG, which is a very good possibility.

As they say in football, the best defense is a good offense.

If the Democrats try to defend themselves from criticism from the IG report by attacking Trump even more, the financial markets are going to suffer.