Keller: How important are endorsements from Taylor Swift and other celebrities?

The opinions expressed below are Jon Keller's, not those of WBZ, CBS News or Paramount Global.

BOSTON - Just moments after Tuesday night's presidential debate ended, pop megastar Taylor Swift threw her support behind Kamala Harris. But will her words influence her millions of followers?

In a social media post, Swift wrote: "I've done my research, and I've made my choice."

300 million Instagram followers

It hasn't been a secret that Swift is not a Donald Trump fan. And it's no surprise that she shares many of Harris' views on women's rights issues. But Swift's endorsement of Harris is still big news because of the reach of her platform - 300 million Instagram followers worldwide - and the way she's using it.

A CBS News poll back in June when Joe Biden was the presumptive nominee found just two-thirds of voters under 30 said they planned to vote this year, well behind older age groups.

So Swift didn't just endorse Harris -- she gave her fans specific details of how to vote and included a link to the vote.gov website that yielded more than 300,000 clicks in just twelve hours.

Importance of Swift's message

Celebrity endorsement expert Megan Duncan, a communications professor at Virginia Tech University, notes how Swift steered her fans toward specific action, "pointing out that especially first-time voters need to make sure that they're registered and reminding people that in many states, early voting is an option."

And consultant Ashley Spillane, author of a recent Harvard study on celebrity impact, observes that Swift didn't just tell her admirers to follow her lead. "She explained her reason for actually making the decision she did and the timing for it, but then she also showed a deep respect for her community and shared with them that they can make their own decision," she said.

Will it pay off?

Will it pay off for Harris?  Gov. Josh Shapiro of crucial swing-state Pennsylvania thinks so: "Her speaking out is a big darn deal."

And so do her fans on the Taylor Swift Subreddit.

"I'm in Pennsylvania and I'm going hard and volunteering with the campaign," wrote one.

Adds another: "I'm a married woman with three kids and a dog…but tonight we are all childless cat ladies!"

What about Trump's celebrity endorsements? The two biggest names at the RNC were Hulk Hogan, who has 2.5 million Instagram followers, and Kid Rock, with 1 million. In terms of sheer reach, no contest.

But today Trump said Swift will "probably pay a price in the marketplace" for endorsing his opponent.

Somehow, I think she can afford it.