Two decades ago, liberals argued that Bill Clinton should not be impeached for his tawdry affair with Monica Lewinsky because, well, his lies were just about sex.

Today, some liberals are arguing that Donald Trump should be impeached because of Stormy Daniels and Karen McDougal because, well, it's not the sex, it's the hush money.

For well over a year, Trump's critics have been banking on Robert Mueller to come up with evidence of Russian collusion, and there have been only disconnected fragments. So now —never mind! — it's about women and money.

The old argument from the left: Trump has committed crimes and should be impeached!

The new argument from the left: Trump has committed crimes and should be indicted!

I'm in no way excusing what went on with the two women from his past. But here's some perspective.

To be sure, Mueller's sentencing memos last week provided some leads on the Russia matter. Michael Cohen, for instance, admitted lying to Congress about the time period that the president's company was pursuing a real estate deal in Moscow, and the memo says Cohen discussed his testimony with people in the White House.

But in the blink of an eye, the media focus seems to be switching to the Stormy narrative — the case being pursued not by Mueller but by the U.S. attorney's office in Manhattan.

Here's a key difference between Trump and Clinton. The 42nd president had his dalliance with Lewinsky while he was in office, in the White House itself, with a subordinate who was a lowly intern. Trump's alleged affairs with a porn star and a Playboy model took place 12 years ago when he was a celebrity businessman.

That's why most people don't care about what Trump did as a private citizen, and I get it. I got a lot of flak when I started reporting on the Stormy case — first broken by the Wall Street Journal days before the election — and always stressed that it was the financial paper trail that might come back to haunt the president.

And that's why the Southern District's probe of Cohen — who was reimbursed for making the $130,000 payment to Daniels and brokered the National Enquirer's $150,000 payment to McDougal — is troublesome for Cohen's former boss.

Yes, it's a campaign finance violation, and yes, those are usually punished by fines or even a slap of the wrist.

But the argument that prosecutors could make is that it was an attempt to subvert the election.

National Review contributor Andrew McCarthy, who worked in the Manhattan U.S. attorney's office and is a sharp critic of the Mueller probe, doesn't mince words in a piece for Fox:

"The president is very likely to be indicted on a charge of violating federal campaign finance laws."

McCarthy's argument is that when Cohen pleaded guilty in August, "prosecutors induced him to make an extraordinary statement in open court: the payments to the women were made 'in coordination with and at the direction of' the candidate for federal office – Donald Trump.

"Prosecutors would not have done this if the president was not on their radar screen. Indeed, if the president was not implicated, I suspect they would not have prosecuted Cohen for campaign finance violations at all. Those charges had a negligible impact on the jail time Cohen faces, which is driven by the more serious offenses of tax and financial institution fraud, involving millions of dollars."

There is, of course, the not-insignificant matter of the Justice Department practice that a sitting president can't be indicted. That's why Democrats like Adam Schiff are now saying Trump could face jail time after he leaves office (if he's not reelected). And MSNBC's Joe Scarborough says the Supreme Court will have to decide whether the president can be indicted for a crime "which helped him get elected."

Trump — proving that no one proofreads his tweets — said: "Democrats can't find a Smocking Gun tying the Trump campaign to Russia." So now, he says, "the Dems go to a simple private transaction, wrongly call it a campaign contribution which it was not (but even if it was, it is only a CIVIL CASE, like Obama's - but it was done correctly by a lawyer and there would not even be a fine. Lawyer's liability if he made a mistake, not me). Cohen just trying to get his sentence reduced. WITCH HUNT!"

All Michael Cohen's fault, according to the president.

I don't minimize the importance of the payments to Daniels and McDougal to suppress their stories before the election. If a Democrat had done that, the right would be up in arms.

But I still think it's a stretch that it leads to indictment or impeachment, especially if the much-ballyhooed Russian collusion probe comes up dry.

And the reason is that the underlying offense (if there is one) was to keep embarrassing sexual disclosures from coming out. The point was to win an election, of course — and the president's pal at the Enquirer's parent company rolled over for him — but also spare Trump pain in his marriage.

My assumption is that much of the public won't see that as sufficient grounds to overturn an election or imprison a president — just as they didn't when Bill Clinton repeatedly lied about a similar subject.