(Reuters) - Pop superstar Taylor Swift’s decision to wade into electoral politics for the first time has driven a spike in online voter registration, particularly among young people, according to the website Vote.org.

The nonprofit site, which helps people register online, reported more than 250,000 new registrations since Swift posted a message on Instagram on Sunday endorsing two Democratic candidates in her home state of Tennessee and urging people to register.

By comparison, the site recorded 57,000 new registrations in all of August and 190,000 last month.

More than 60 percent of the registrations since Sunday were among voters between 18 and 29 years old, an increase the site said was likely prompted by Swift’s post.

“This is a pretty incredible, off-the-charts event,” said Raven Brooks, the chief operating officer for Vote.org.

Vote.org acknowledged it was not possible to measure the direct impact of Swift’s move, but Brooks noted the surge in young voters was in line with Swift’s youthful fan base.

Swift’s enormous reach - a best-selling album and tour as well as 112 million Instagram followers - underscores the way celebrities can leverage their online presence.

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Swift on Tuesday won four awards, including artist of the year, at the American Music Awards in Los Angeles and again urged fans to vote, but without declaring any party interest.

Grammy winner Rihanna in an Instagram post urged fans to register to vote on Tuesday - the last day in 14 states for citizens to do so.

TIGHT TENNESSEE RACE

Polls show the U.S. Senate contest between Democrat Phil Bredesen and Republican Marsha Blackburn, a staunch supporter of President Donald Trump, virtually tied in a state Trump won by 16 points in 2016.

Swift, who has eschewed politics, told her followers she could not support Blackburn due to the congresswoman’s record on women’s issues and gay rights.

Politics can be dicey for artists such as Swift with roots - and fans - in country music, the dominant genre of red state America.

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President Donald Trump on Monday called Swift an uninformed voter. “Let’s just say I like Taylor’s music about 25 percent less now, OK?,” he told reporters.

Former Arkansas Governor Mike Huckabee also chimed in saying her endorsements “won’t impact the election unless we allow 13 yr old girls to vote.”

Many celebrities identify as liberals, and Democrat Hillary Clinton enjoyed broad support from actors, musicians and other popular figures in 2016.

The most notable celebrity to support Trump may be the rapper Kanye West, who will have lunch with the president at the White House on Thursday.

West and Swift engaged in a years-long feud after West interrupted Swift’s acceptance speech at the 2009 MTV Video Music Awards.