Kaine, the onetime running mate of Democrat Hillary Clinton, followed that advice to a fault, according to post-debate analysis from 2016. He interrupted Trump running mate Mike Pence dozens of times, creating the impression that Pence was in control and Kaine rattled or nervous.

Still, Kaine kept the focus on former President Donald Trump and away from Clinton, loading his answers with reminders of Trump’s past controversial remarks.

“You can’t let your opponent take shots at your top of the ticket. You got to be the goaltender, and you got to block all the shots or maybe keep pressure on the other guy,” Kaine told the Washington Examiner.

Kaine, who lost to Trump and Pence in a stunning upset, doubted the debate will matter on Election Day given the secondary role candidates for vice president play on the campaign trail.

Most criticism was laid at the feet of Clinton, who underestimated Trump’s ability to crack blue wall states such as Wisconsin.

But Kaine does see a danger in Walz spending too much time protecting his own image, singling out the late Sen. Joe Lieberman’s desire for civility in his 2000 debate against Dick Cheney, the Republican vice presidential nominee.

His boss, Al Gore, ultimately lost to President George W. Bush that November.

“Look, I was a friend of Joe’s, but his strategy was to make people like him, not to protect Gore,” Kaine said. “And so, Cheney took a lot of shots on goal against Gore during that debate, and Lieberman didn’t really protect him.”

The advice is, at its core, a reminder to play attack dog, from one “nice guy” to another. Vice President Kamala Harris chose Walz, in part, for his affable, Midwestern demeanor. 

It also reflects the conventional wisdom that vice presidential debates won’t help, but can hurt, the ticket.

“The debate doesn’t really move anything unless you don’t protect your top of the ticket,” Kaine said.

Walz will meet Vance on Tuesday at a precarious moment in the race. Democrats reset the electoral map when President Joe Biden dropped out, replacing him instead with the younger Harris. But Trump is still running neck and neck with her in virtually every swing state.

Kaine expects that Vance will try to jab Walz a couple of times to “get under his skin.” He often accuses Walz of lying about his military service.

Walz, for his part, painted Vance as a coastal elite over the weekend because of his stint in venture capital.

But Vance has generally kept his sights on Harris, and Kaine predicted that will be his approach on Tuesday.

Kaine has not been advising Walz on debate preparations. That responsibility has fallen to Transportation Secretary Pete Buttigieg, who is playing Vance in mock sessions.

Meanwhile, Vance chose House Majority Whip Tom Emmer (R-MN) as his Walz stand-in.

Kaine, up for reelection in November, is preparing for his own Senate debate in Virginia, to be held one day after Walz’s.

He is facing Republican Hung Cao in a race that Cook Political Report rates solidly in Democrats’ favor.

“I’m doing one practice debate, and then I will just be myself,” Kaine said of his preparations.