Former Congressman Beto O'Rourke of Texas announced Friday he is dropping out of the presidential race. "Though it is difficult to accept, it is clear to me now that this campaign does not have the means to move forward successfully," O'Rourke wrote, announcing his decision on Medium.

"This a campaign that has prided itself on seeing things clearly and speaking honestly and acting decisively," O'Rourke told emotional supporters after the announcement. "We have to clearly see at this point that we do not have the means to pursue this campaign successfully and my service will not be as a candidate nor as the nominee for this party for the presidency."

O'Rourke told supporters that although "this is the end of the campaign, we are right in the middle of this fight." He said he will "do everything I can to support the eventual nominee of this party with everything I've got and I encourage every single one of you to do the same." He vowed to be part of "all the same causes that brought us here," including gun control, climate change and structural racism.

Although O'Rourke had been struggling recently, he had been scheduled to speak Friday night at the Iowa Democratic Party dinner along with the other candidates in the race. He was also scheduled to file his official candidacy in New Hampshire next week.

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"I decided to run for President because I believed that I could help bring a divided country together in common cause to confront the greatest set of challenges we've ever faced," O'Rourke wrote in his Medium post. "I also knew that the most fundamental of them is fear — the fear that Donald Trump wants us to feel about one another; the very real fear that too many in this country live under; and the fear we sometimes feel when it comes to doing the right thing, especially when it runs counter to what is politically convenient or popular."

President Trump mocked O'Rourke in a tweet, writing "Oh no, Beto just dropped out of race for President despite him saying he was 'born for this.' I don't think so!"

Outside the arena hosting Friday's major Democratic Party event, O'Rourke supporters had remained gathered at a spot where the candidate planned to address them. Before his arrival, some volunteers began pulling lawn signs out of the ground. When a CBS News team converged to document the scene, a O'Rourke campaign staffer approached and asked that we stop and be "respectful" because the volunteers "are very vulnerable right now."

O'Rourke had not yet qualified for the November debate, which has become a make-or-break marker for many of the Democrats. But despite struggling in the polls, CBS News' Battleground Tracker estimated in September that he could pick up some delegates in the primary due to his support in Texas.

A spokesman for O'Rourke told The New York Times that O'Rourke will not be running for a Senate seat. There had been public pressure for him to challenge Republican John Cornyn in 2020.

"Beto will not be a candidate for U.S. Senate in Texas in 2020," Rob Friedlander, an aide to O'Rourke, told The Times.

A three-term Congressman from El Paso, O'Rourke was a rising star after the 2018 Senate race, where he won more votes than any other Democrat in Texas history. After the unexpectedly close race, Democrats nationally started talking about turning Texas blue, a feat that would have seemed impossible even as recently as 2016.

O'Rourke jumped into the race with much fanfare, including a Vanity Fair cover — that would later be mocked — where he said he was "born to be in it." He raised $6.1 million in the first 24 hours of his campaign, which set a record at the time and would only be beaten by former Vice President Joe Biden, who raised $6.3 million.

But his campaign struggled early with staffing problems and messaging. O'Rourke began lagging in the polls and his fundraising suffered, and he raised just $3.6 million between April and the end of June. He had similar problems in the next three months, raising only $4.5 million. O'Rourke, who was a fundraising superstar in the Texas Senate race, refused to accept PAC money for the presidential race, meaning he relied heavily on grassroots support — although he did hold some private fundraisers.

After the shooting in El Paso that left 22 dead, O'Rourke took a break from campaigning to help his community heal. But he unexpectedly went viral for an expletive-laced tirade with a reporter about media coverage and Mr. Trump.

O'Rourke began working aggressively to champion stricter gun control laws, and signed on to mandatory buybacks of AR-15s and AK-47s. His blunt messaging about guns led him to become a target of the NRA, which began calling him the "AR-15 salesman of the year."

O'Rourke had a standout moment at the next debate when he declared "hell yes, we're going to take away your guns!" A Texas state lawmaker tweeted at him "My AR is ready for you Beto," which the campaign then reported as a threat.

The comment drew applause at the time and praise from some Democrats — but others, most notably South Bend Mayor Pete Buttigieg, criticized him for going too far. O'Rourke spent time during and after the debate sparring with Buttigieg, who favors more moderate gun control measures.

At the same time as Mr. Trump's rally in Dallas two weeks ago, O'Rourke held a counter-rally a few miles away. According to O'Rourke's campaign, there were over 5,000 people in attendance at that rally, during which O'Rourke called out what he described as the "false, bullsh*t fear of Donald Trump."

Mr. Trump targeted O'Rourke during his own rally. Mr. Trump called O'Rourke "a very dumb Democrat candidate for president," and tore into the 2020 contender for his stance on guns and his proposal to end tax exemptions for religious organizations that oppose same-sex marriages.

"Beto, in a few short weeks, got rid of guns and got rid of religion," Mr. Trump said. "Those are not two good things in Texas to get rid of."

In an interview with CBS News last week, O'Rourke defended his gun control plan, saying that anyone who refuses to go along with his mandatory buyback, should it become law, will face "consequences."

"If we're able to pass mandatory buybacks and I'm able to sign that into law, then I fully expect our fellow Americans to turn in their AR-15s and their AK-47s," O'Rourke said.

Ed O'Keefe contributed to this report.