Guthrie said it's difficult to credit Swift directly for the spike in registrations because there is usually some kind of a surge just before voter registration deadlines, in election years, since "people wait until the deadline to register." (As is the case in many states, Tuesday is the deadline to register to vote in Tennessee in time for the Nov. 6 election. )
However, among the 169,000 new registrations since Sunday, more than half were by those ages 18 to 29.
"One thing is clear, we're seeing a massive surge in the 18-24 and 25-29 voters, which is her fan demographic. The 18-24 number almost doubled overnight," Guthrie said. "Taylor Swift's visibility on this issue is driving a lot of coverage of voter registration and it's reaching many of her fans who would not otherwise be following news like this."
Vote.org also saw a definite jump in traffic in the wake of her Instagram post. The site typically has 14,078 average daily visitors, Guthrie said. In the 24 hours after Swift's post - which specifically mentioned Vote.org - the site had 155,940 visitors.
In Tennessee, where Swift is registered to vote, Vote.org tracked 2,144 new voter registrations in the 36 hours since the singer's post, bringing October's to-date total to 7,554 - a sharp increase from 2,811 registrations in September and 951 in August.
"Overall, we were thrilled, especially to see millennials get involved," Guthrie said. "Taylor's post has helped bring out young voters. ... We're especially happy to see that because we know voting is habit-forming; statistically, a young person who votes in 2018 is 55 percent more likely to vote again in 2020."
In her post Sunday, Swift vowed to vote for two Democratic candidates: former governor Phil Bredesen for the U.S. Senate and Rep. Jim Cooper for re-election. She also acknowledged her past reluctance to address political issues but said that had changed in the past two years:
"I always have and always will cast my vote based on which candidate will protect and fight for the human rights I believe we all deserve in this country," she wrote. "I believe in the fight for LGBTQ rights, and that any form of discrimination based on sexual orientation or gender is WRONG. I believe that the systemic racism we still see in this country towards people of color is terrifying, sickening and prevalent."
Swift also blasted Rep. Marsha Blackburn, Bredesen's Republican opponent, for having voted against those values.
"As much as I have in the past and would like to continue voting for women in office, I cannot support Marsha Blackburn," Swift wrote. "Her voting record in Congress appalls and terrifies me."
Swift implored her followers to "please, please educate yourself" on their local candidates and to vote.
"For a lot of us, we may never find a candidate or party with whom we agree 100 percent on every issue, but we have to vote anyway," Swift wrote. "So many intelligent, thoughtful, self-possessed people have turned 18 in the past two years and now have the right and privilege to make their vote count."
Swift's Instagram post was welcomed by Democrats in Tennessee, where polls show Blackburn and Bredesen are in a tight race to replace Republican Sen. Bob Corker.
President Donald Trump, who has hailed Blackburn as an "outstanding person & great supporter of mine," brushed off Swift's Instagram post Monday night.
"I'm sure Taylor Swift doesn't know anything about (Blackburn)," Trump said. "Let's say that I like Taylor's music about 25 percent less now, OK?"
On Monday, Trump tried to mobilize his own followers by retweeting a message indicating Tuesday was the deadline to register to vote in more than a dozen states.
"REGISTER TO VOTE!" the president noted, followed by a link to a voter registration site run by the GOP.
