Last week, President Trump and his lawyer Rudolph W. Giuliani argued that collusion isn't a crime. But on Monday, Trump suggested that Hillary Clinton should be investigated for this supposed non-crime.

“Collusion is very real with Russia,” Trump quoted conservative commentator Dan Bongino as saying on Trump's favorite Fox News morning show, “but only with Hillary and the Democrats, and we should demand a full investigation.”

Investigations, it bears emphasizing, are generally launched to find illegal activity. Trump's call to investigate Clinton's alleged collusion with Russia — a complex and strained theory having to do with the Steele dossier — would seem to belie his true opinion about whether collusion is, in fact, a crime.

But it's hardly the first time he's admitted the obvious: that while the word “collusion” doesn't appear in the criminal code, it is synonymous with and related to very real crimes. Over and over, mostly through his allegations of Democratic collusion, he's acknowledged the criminal nature of collusion in ways that would seem to make it much more difficult for his lawyers to press the case that collusion by Donald Trump Jr. or anybody else wasn't criminal.

Here are five examples.

1. Another call for investigating Democrats

Back on June 8, Trump suggested that Democrats should be probed for collusion and obstruction of justice.

“Now, the Democrats have had massive collusion, massive obstruction, and they should be investigated,” Trump said.

2. Mueller should look into “all of the criminal activity & real Russian Collusion on the Democrats side”

In the same vein as above:

3. Collusion is part of what makes Clinton “CROOKED”

Here, Trump includes “collusion” while talking about Clinton being “CROOKED.” Corruption is generally understood as illegal activity.

4. Clinton colluded with the Justice and State departments

Late in the 2016 campaign, Trump accused Clinton of “collusion” with the Justice Department and State Department, which he labeled “possibly illegal.”

And through WikiLeaks today, it's just been shown that this is, as I've been saying, a rigged system with more collusion — possibly illegal — between the Justice Department, the Clinton campaign and the State Department,” Trump said. “Right?”

At another point, Trump said this collusion amounted to corruption, which again connotes illegality.

“This shows corruption at the highest level, and we can't let it happen as American citizens,” Trump said.

5. Cruz and Kasich engaged in “illegal collusion”

Trump called Sen. Ted Cruz (R-Tex.) and Ohio Gov. John Kasich working together to prevent him from winning primaries  “illegal collusion” and noted that collusion is illegal in business.

“It shows total weakness, it shows illegal collusion,” he said. “You know, in business, you get put in jail [for that].”