Image copyright Getty Images Image caption The pair are backing opposing sides in the 2018 mid-term elections

Music's most notorious on-off feud - Taylor Swift versus Kanye West - has officially turned political.

Swift, who has long resisted going public on her politics, came out in favour of two democratic candidates in her home state of Tennessee in the upcoming mid-term elections on Sunday.

West meanwhile is a well-known and outspoken supporter of President Donald Trump, and will meet the Republican in the White House this week for lunch.

Their involvement has sparked a debate across the US political spectrum about celebrities and political endorsements.

It's all a bit surreal... so let's re-cap on the drama so far.

2009: The feud ignites

It all began in September 2009 at the MTV Video Music Awards at the Radio City Music Hall in New York.

Image copyright Getty Images Image caption The 2009 award was Swift's first Video Music Award

A 19-year-old Swift had just defeated Beyoncé to win Best Female Video for her country-pop teen anthem You Belong With Me when West notoriously jumped on stage and interrupted her, mid-acceptance speech.

"Yo Taylor, I'm really happy for you, I'ma let you finish, but Beyoncé had one of the best videos of all time! One of the best videos of all time!" he declared to millions watching.

Beyoncé looked incredulous, the crowd booed and Swift looked lost, reportedly leaving the stage in tears.

Later in the ceremony, Beyoncé invited Swift back on stage to "have her moment". On the Jay Leno show two days later, West admitted he was rude.

Media playback is unsupported on your device Media caption The Kanye West moments that shocked us

He apologised several times but the moment stuck, and even President Barack Obama labelled him a "jackass" over it.

2010: Kanye apologises

In a lengthy Twitter-storm in September 2010, West again apologised and said he had written a song for Swift, before deleting his account.

But just days later, Swift debuted her track "Innocent" at the 2010 VMAs with lyrics taking a dig at West: "Thirty two and still growin' up now// Who you are is not what you did // You're still an innocent."

West then seemed to back-track on his apology, accusing Swift of riding the wave of the VMA fall-out for publicity.

2013: Kanye un-apologises

Days before he became a father for the first time with partner Kim Kardashian, West gave an extensive interview with the New York Times newspaper when he declared he had no regrets over the Swift incident.

Image copyright Getty Images Image caption West and Kim Kardashian began in dating in 2012

"If anyone's reading this waiting for some type of full-on, flat apology for anything, they should just stop reading right now," he said.

He also said the previous apologies were down to "peer pressure".

2015: BFFs?

By 2015, the feud looked well and truly put to bed. West hinted they would work on music together and Kardashian attended a Swift concert in London with sister Kendall.

The three appeared cosy on that year's award ceremony circuit and at the VMAs Swift quoted and mocked his infamous interruption on-stage when presenting West the special Video Vanguard Award.

Image copyright Getty Images Image caption West sent Swift flowers after the ceremony, which she posed with online in a now-deleted post

Swift even joked on social media about being West's running-mate after he appeared to announce his intention to run for president in 2020 during his acceptance speech.

2016: The feud reignites

Everything changed when West released his (now infamous) track "Famous" in February 2016.

The song contained the lyrics: "I feel like me and Taylor might still have sex// Why? I made that bitch famous"

After the line drew criticism, West defended it on Twitter, saying he was complimenting and actually quoting the pop star.

"I called Taylor and had a hour long convo with her about the line, and she thought it was funny and gave her blessings," he tweeted.

But Swift's representatives hit back, insisting she was not told about the bitch line and had "cautioned him about releasing a song with such a strong misogynistic message".

Image copyright Getty Images Image caption The pair appeared to be on good terms in 2015

When Swift scooped the Grammy for Album of the Year just weeks later for her album 1989, she unleashed a thinly-veiled dig back at West.

"There are going to be people along the way who try to undercut your success or take credit for your accomplishments or your fame - but if you just focus on the work and you don't let those people sidetrack you, someday when you get where you're going, you'll look around and you will know that it was you, and the people who love you, who put you there - and that will be the greatest feeling in the world," she said in her speech.

In a July cover-interview with GQ magazine, Kardashian retorted, again insisting Swift had "totally approved" Famous.

"She wanted to all of a sudden act like she didn't. I swear, my husband gets so much [expletive] for things [when] he really was doing proper protocol and even called to get it approved," she told the magazine.

Image copyright Getty Images Image caption Earlier this year, Kardashian sent bottles of her perfume to her "haters" including Swift

She also said there was a recording of the call, and alleged Swift's lawyer had told them to destroy it.

West then dropped the music video for the song, which was even more inflammatory than the lyrics.

It featured a hyper-realistic model of Swift naked in a giant bed alongside other figures such as President Trump, George W. Bush, Rihanna and Vogue Editor Anna Wintour (along with Kanye, Kardashian and two of their exes).

Kardashian then released the footage of the alleged phone call and trolled Swift with lots of snake emojis, which fans followed suit in.

In a now-deleted post, Swift again insisted she was not aware of the bitch line and accused the two of "character assassination".

"I would very much like to be excluded from this narrative, one that I have never asked to be a part of, since 2009," she ended the statement.

2017: Look What You Made Me Do

Swift cleared her Instagram account ahead of the release of her sixth studio album Reputation and teased the release with videos of snakes - embracing the animal in her promotion and tours as a new mascot.

Her single Look What You Made Me Do announced the old Taylor was "dead" and featured lyrics that many believed alluded to the West feud: "The world moves on // Another day another drama, drama // But not for me, not for me // All I think about is karma."

The video for the song broke YouTube records, took on her critics and poked fun at herself. It also featured the singer wearing her 2009 VMA outfit, repeating the "narrative" exclusion line from the statement.

2018: What next?

Apparently now at opposite ends of the political spectrum, a reunion for that 2020 run doesn't look likely any time soon.

But how seriously should we be taking them both politically?

Vote.org told Buzzfeed News that Swift's post on Sunday to her 112m Instagram followers led to a spike in voter registrations - with 65,000 signing up in just 24 hours.

The Wests don't look to be shying away from the political arena any time soon either.

Image copyright SOPA Images Image caption Kardashian and West attended the March For Our Lives event in Washington in March with their daughter

Kardashian took a case for clemency direct to the White House earlier this year, which led to 63-year-old grandmother and convict Alice Johnson being granted early release.

The reality star has said she wants to do more political advocacy work and has also spoken out in favour of Planned Parenthood and against gun violence on her family's hit reality show in the past.

West was first spotted in Trump Tower meeting then president-elect Donald Trump in 2016.

But in the last couple of weeks alone he has been spotted multiple times wearing a Make America Great Again hat, spoke out in defence of the president on Saturday Night Live, deleted his social media accounts (again) and is now set for a White House lunch visit.

So who knows what will happen next?