Paul Newman, who died Friday, was a very serious guy, but he also had a playful side.

I remember tooling along with him in his Volkswagen Bug, which was equipped with a powerful Porsche engine. He would pull alongside a sharp sports car on the upward slope of the 405 Freeway, then blast forward, leaving the other driver trying to figure out how a Bug could possibly leave him in its dust.

But Newman also had been radicalized by Vietnam and Nixonian politics, and he and his wife, Joanne Woodward, were ready and willing to use their clout to advance their political positions. That ultimately was to lead us into conflict.

Newman wanted Paramount to make a political film titled “WUSA” — a project that I truly hated. Paramount had released other “message” movies that had proved to be flops, including a turgid tome called “The Molly Maguires,” set in the coal mines (it starred Sean Connery and Richard Harris). As Paramount’s vice president for production, I felt strongly that pricey political films would kill the studio, which was already in fragile shape.

I’m embarrassed to admit it, but at the time, I subscribed to Sam Goldwyn’s dictum that “if you have a message, send it through Western Union.”

Well, that didn’t go well with Paul and Joanne Newman. They felt “WUSA” had an important message about corporate corruption of the media and were indignant that I didn’t see it their way. They lobbied Bob Evans, who agreed with me. They then lobbied Paramount’s corporate leaders in New York, who succumbed to their passionate persuasion. Their movie went forward.

“I don’t get you,” Newman told me as the film started shooting. “There aren’t many smart people who have power. And you have to use your power to advance truth. What’s money and power worth if you don’t do that?” He wasn’t being vengeful or petulant. Indeed, he said it all with his usual wry smile. And those amazing blue eyes were making direct contact.

“WUSA” was a terrible flop. But I took no satisfaction from having been right in my dire forecasts. I deeply admired Newman for following his convictions.

And he paid the price. His career lost a lot of its heat in the ’70s. He was still a big star but, for a while, his box office magic had faded.

To the end, Newman adhered to his beliefs. He could always be counted on to help causes he believed in, and they were usually on the left.

And to the end, he was, and will remain, Hollywood’s perfect leading man.