The presumptive Democratic candidate announced his VP running mate Tuesday, and the choice is historic. Harris will become the first black female vice presidential candidate in the history of this country.

Biden appeared to signal Harris as his running mate back in July, when a reporter got a peek at his cheat sheet during a news conference and at the tip, it had Harris' name with the words ... "don't hold grudges."

Of course, the "grudges" note references their first debate, where Harris attacked Biden for his stand against school bussing ... something that Harris benefited from during her school days.

Harris was in a somewhat unique position among the various women Biden was considering. She has executive experience, both as a District Attorney and California Attorney General. That's a huge asset for Biden, and for voters.

Given Biden's age, a Veep who can step into the role is a reality and, some say, a necessity.

It's interesting ... just Monday, Charlamagne and Diddy warned Biden ... if he didn't pick a black female, he'd lose the election.

The one problem Biden has with Harris ... both have been criticized for their stance on crime. Biden's support of the '94 crime bill had dogged him, while Harris took some shots during the debates over prosecuting marijuana cases which disproportionally affected African-Americans.

Biden's big decision comes ahead of a big week for the Dems ... the Democratic National Convention kicks off Monday, and Biden will accept the party's nomination Thursday from Delaware, where he will deliver his virtual acceptance speech.

Now, buckle up and wait for President Trump to tweet about Biden's pick in 3 ... 2 ... 1.