His track record during six years in the US House of Representatives is thin.
Last month the former congressman from El Paso said he would "absolutely" support tearing down existing barriers along the southern border with Mexico.
'I want to be in it, ' he adds.
Unlike many of his opponents who launched campaigns while barely registering in public opinion polls, O'Rourke begins in sixth place in the RealClearPolitics average of polls, receiving an average of 5 percent.
"CBS This Morning" co-anchor Gayle King will speak with O'Rourke for his only national TV interview following his 2020 announcement, Friday on "CBS This Morning" with a preview airing on "CBS Evening News" Thursday night.
O'Rourke joins a crowded field of more than a dozen Democrats as a wildcard.
Some Democrats criticized that unorthodox strategy, as other top White House hopefuls were building national and state teams and making numerous early state visits.
O'Rourke, a former three-term USA congressman and a punk rocker in his youth, pledged to tackle "the interconnected crises in our economy, our democracy and our climate".
The cover has already gotten the meme treatment, too.
O'Rourke, whose given name is Robert Francis, acquired his nickname while growing up in El Paso, Texas. He has a unique backstory that includes stints in punk rock bands.