President Donald Trump now likes Taylor Swift “25 per cent less” after the pop star broke her political silence and revealed she was backing two Democratic candidates for the upcoming US mid-term elections.

Trump hit back at Swift a day after the 28-year-old singer-songwriter endorsed Democratic candidate Phil Bredesen, a former governor, over Republican Marsha Blackburn in her home state of Tennessee’s Senate race.

“I’m sure Taylor Swift has nothing — or doesn’t know anything about her (Blackurn),” Trump said when told about Swift’s political leanings.

“Let’s say that I like Taylor’s music about 25 per cent less now, OK?” Trump was quoted as saying by the CNN.

Swift endorsed Democrats Bredesen and Jim Cooper for the November 6 midterm polls in a long Instagram post on Sunday, breaking her years-long policy of keeping her politics to herself.

“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,” she wrote.

Swift criticised Republican Senate nominee Blackburn for her voting record on gender equality.

“Her voting record in Congress appalls and terrifies me,” she wrote, citing the politician’s votes against equal pay and domestic violence legislation.

Speaking outside the White House on Monday, Trump told reporters, “Marsha Blackburn is doing a very good job in Tennessee. She’s leading now, substantially, as she should. She’s a tremendous woman, I am sure Taylor Swift does not know anything about her.”

In his previous tweets posted in 2012, the US President described Swift as “fantastic” and “terrific” and had thanked her for taking a picture with him.

“Thanks for the beautiful picture — you are fantastic!” Trump had said in a tweet in 2012.