In recent months Donald Trump has been trading insults with the Clintons. But before the presidential race began, they enjoyed a much more cordial relationship. (Peter Stevenson,Deirdra O'Regan/The Washington Post)

This post has been updated.

On Thursday morning, Donald Trump upped the ante in his ongoing back and forth with Hillary and Bill Clinton by releasing this Instagram video detailing some of the lowest moments for the former first family and their friends.

Hillary and her friends!

A video posted by Donald J. Trump (@realdonaldtrump) on

Monica Lewinsky. Anthony Weiner. Bill Cosby! All overlaid on Hillary Clinton's famous assertion in China in 1995 that "human rights are women’s rights and women’s rights are human rights."

The video, which as of this writing already had almost 7,000 "likes" on Instagram, will undoubtedly get extended airtime this afternoon and tonight on cable television. And it will force the Clinton campaign to respond in some shape or form - which she did, sort of, via Twitter Thursday afternoon.

Unlike many of Trump's other fights — over John McCain's POW status, Megyn Kelly, Fox News — attacking the Clintons is a conventional — and smart — strategy in a Republican primary.

Hillary Clinton is deeply unpopular among self-identified Republicans. Just 15 percent of Republicans had a favorable opinion of Clinton in Washington Post-ABC News polling done in the fall. Given those numbers, it's hard for any Republican to go wrong attacking the Clintons.

And it's hard to "go too far" in those attacks — at least in the eyes of GOP voters. Lots and lots of Republicans believe that the Clintons have never truly been called out for how they acted in public office and never been properly shamed for their behavior. Attacking Bill Clinton for his admitted extramarital affair with Monica Lewinsky or noting that Weiner, a Clinton friend, was sending salacious pictures of his privates to women on the Internet is not only considered fair game but is also applauded by the very voters Trump wants and needs if he is going to be the Republican presidential nominee.

Former president Bill Clinton spoke in New Hampshire on Jan. 4, his first speech in support of his wife, Democratic front-runner Hillary Clinton, in 2016. (The Washington Post)

The "attack Clinton" strategy also hews to a strategy that has earned Trump broad support among GOP voters: He says what he believes and believes what he says. Trump doesn't apologize — no matter the blowback. He's the opposite of politically correct, a very good place to be in an environment in which large numbers of Republicans believe that liberal-led political correctness is destroying society.

As always with Trump, it's hard to know how much of what he does is the result of well-thought-out political calculation and how much is simply him saying, "Let's do a video with Monica, Weiner and Cosby in it!"

Regardless, his strategic antenna — even when it has operated directly against conventional wisdom — has been perfectly tuned for the majority of this race. His decision to up the attack on the Clintons — and, in particular, Hillary's position as a leader on women's rights — makes perfect sense from a conventional political perspective. Which, if past is prologue with Trump, means it won't work.