By comparison, the site recorded 57,000 new registrations in all of August and 190,000 last month.
Following Swift's endorsements, President Trump told reporters on Monday that he likes her music "about 25 percent less". "I believe in the fight for LGBTQ rights, and that any form of discrimination based on sexual orientation or gender is WRONG".
Kamari Guthrie, director of communications for the nonprofit Vote.org, told Buzzfeed that numbers had spiked both nationally and in Swift's home state of Tennessee after the singer's post Sunday on Instagram.
Blackburn has not responded to the message nor Swift's assertion that her voting record is anti-woman and anti-equality.
Taylor Swift recently posted a lengthy and candid post about her political involvement to her Instagram telling her followers, "In the past I've been reluctant to publicly voice my political opinions, but due to several events in my life and in the world in the past two years, I feel very differently about that now".
Swift, 28, noted Blackburn's voted against equal pay for women, against reauthorizing the Violence Against Women Act that protects women from domestic abuse, and opposes marriage equality.
The registration deadline is Tuesday in Tennessee and more than a dozen other states.
President Trump, naturally, weighed in on the matter: "I'm sure Taylor Swift doesn't know anything about [Blackburn]". She believes businesses have a right to refuse service to gay couples. "But people would still rather believe that she is the one who is pushing Trump's agenda".
Of the roughly 240,000 people who have registered on Vote.org for the upcoming midterm elections on November 6, almost half, or about 102,000, are between the ages of 18 and 29, the website found.
Swift, 28, has notably stayed out of the US political fray in contrast to her more vocal peers, like Democratic supporters Katy Perry and Beyoncé, and Republican backer Kid Rock.
10 interesting facts about pop star Taylor Swift. She represented Tennessee's 7th congressional district. "Lets say that I like Taylors music about 25 percent less now, OK?"