Beto O’Rourke has formally announced that he will seek the 2020 Democratic presidential nomination, ending months of intense speculation over whether he'd try to translate his newfound political celebrity into a White House bid.

"This is going to be a positive campaign that seeks to bring out the very best from every single one of us, that seeks to unite a very divided country," O'Rourke said in a video announcement with his wife on a couch. "We saw the power of this in Texas."

Mr O'Rourke promises in the video posted Thursday: "I'm going to travel this country and listen to those I seek to serve" and then will return to El Paso on March 30 for a campaign kickoff. He invites would-be supporters "to the greatest grassroots campaign this country has ever seen."

The 46-year-old who gained a national following with his long-shot election battle against Senator Ted Cruz last year had earlier told the KTSM news channel: ”I’m really proud of what El Paso did and what El Paso represents.

“It’s a big part of why I’m running. This city is the best example of this country at its best.”

The former three-term US congressman ​was a heavy underdog when he challenged Mr Cruz, a Republican in mostly conservative Texas, but he quickly demonstrated an ability to draw capacity crowds and raise money from voters nationwide. His candidacy also generated a torrent of media coverage.

Who could be running against Trump in 2020? Show all 23 1 /23 Who could be running against Trump in 2020? Who could be running against Trump in 2020? Joe Biden The former vice president - poised to be a frontrunner - has announced his run. He recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well AFP/Getty Who could be running against Trump in 2020? Bernie Sanders The 2016 runner-up has announced that he will be running again in 2020 Getty Who could be running against Trump in 2020? Hillary Clinton The 2016 Democratic presidential candidate and former Secretary of State says she is “still considering” whether she will run again. Getty Who could be running against Trump in 2020? Pete Buttigieg The Indiana mayor and war veteran will be running for president. If elected, he would be the first openly LGBT+ president in American history. Getty Who could be running against Trump in 2020? Kamala Harris The former California attorney general will be running for president in 2020. Introduced to the national stage during Jeff Sessions’ testimony, she has endorsed Medicare-for-all and proposed a major tax-credit for the middle class. AP Who could be running against Trump in 2020? Elizabeth Warren The Massachusetts Senator has formally launched her bid for president in 2020. A progressive Democrat, she is a major supporter of regulating Wall Street. AP Who could be running against Trump in 2020? Beto O’Rourke The former Texas congressman told Oprah Winfrey that he “has been thinking about running for presidency”, but stopped short of formally announcing his bid to run in 2020. AFP/Getty Who could be running against Trump in 2020? Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam has announced his bid. He intends to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord. Vice News Who could be running against Trump in 2020? Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege.” Getty Who could be running against Trump in 2020? Cory Booker The New Jersey Senator has announced that he will be running for the presidency in 2020. If he secures the nomination he said finding a female vice president would be a priority. Getty Who could be running against Trump in 2020? John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017. AP Who could be running against Trump in 2020? Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US. Getty Who could be running against Trump in 2020? Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but is likely to face tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad. Getty Who could be running against Trump in 2020? Andrew Yang The entrepreneur has announced his presidential candidacy, and has pledged that he would introduce a universal basic income of $1,000 a month to every American over the age of 18. AFP/Getty Who could be running against Trump in 2020? Marianne Williamson The author and spiritual advisor has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful. Getty Who could be running against Trump in 2020? John Kerry The former secretary of state has said he is still thinking about whether to run. Getty Who could be running against Trump in 2020? Michael Bloomberg The entrepreneur and former New York mayor– with a net worth of around $50bn – has said he will decide by the end of February whether to seek the presidency. AFP Who could be running against Trump in 2020? Howard Schultz Former Starbucks CEO Howard Schultz has not yet ruled out running for president in 2020, despite criticism that his bid could help re-elect Mr Trump by dividing the Democrat vote. AP Who could be running against Trump in 2020? Eric Holder The former attorney general has said he will decide in “the next month or so” whether to run as a 2020 presidential candidate. AP Who could be running against Trump in 2020? Eric Swalwell The California congressman said he is “ready to do this” and will decide before April whether to run. MSNBC Who could be running against Trump in 2020? Terry McAuliffe The former Virginia governor, who worked to elect Democratic governors during 2018 midterms, said there was a “50 per cent” chance he would run. AP Who could be running against Trump in 2020? Sherrod Brown The Ohio senator is still undecided about whether to run for president in 2020. Who could be running against Trump in 2020? Mitch Landrieu The former New Orleans mayor said he doesn’t think he will run for president, but “never say never”. AP Photo/Jacquelyn Martin

Early opinion polls on the 2020 race have consistently ranked him in the top tier of contenders, behind former vice president Joe Biden, who has not yet said whether he is running, and veteran Vermont senator Bernie Sanders.

This weekend Mr O’Rourke is to campaign in the politically crucial state of Iowa alongside Eric Giddens, who is running in a special election for a state senate seat.

His communications director tweeted: “Beto will be in Waterloo on Saturday to kick off an afternoon of canvassing, [get out the vote] and grassroots organising for state senate candidate Eric Giddens.”

Earlier, Mr Giddens had tweeted a video of the Texan wearing a University of Northern Iowa hat and encouraging students to support the fellow Democrat in the upcoming race.

“Supporting him for state senate is the way that we get Iowa, and by extension, this country, back on the right track,” Mr O’Rourke says. “We’re counting on you, and we’re looking forward to seeing you soon. Adios.”

Iowa, which holds its primary election, or caucus, in January 2020, the first in the nationwide election cycle, is a crucial test for anyone seeking the presidency, as it the first time voters cast actual ballots on candidates.

It has been the making of many campaigns.

Donald Trump ran a narrow second to Ted Cruz there in 2016 – while it has also been a graveyard for others. In the same cycle, Bernie Sanders’s campaign was boosted when he almost beat Hillary Clinton – she won 49.8 – 49.5 – while Martin O’Malley, a governor of Maryland whom many believed was an attractive candidate, dropped out to the race after winning barely 0.5 per cent of the vote.

Since his Senate bid ended, Mr O’Rourke has worked to keep himself in the public eye, regularly staying in touch with his supporters and sitting for an interview with Oprah Winfrey.

He took a well-publicised road trip across the American Southwest, stopping at colleges and diners and he visited students in the key swing state of Wisconsin.

He also held a rally in El Paso on the same night in February that Mr Trump staged one there.