He is expected to immediately set out on a campaign swing through Iowa, which holds the first Democratic nominating contest in February 2020. Which current candidate has the most to fear from his run?
"They will either consume us, or they will afford us the greatest opportunity to unleash the genius of the United States of America", he added.
Prior to his Senate bid, O'Rourke had kept a relatively low profile as a three-term congressman with little name recognition. "It's a big part of why I'm running".
Speculation about his plans had already increased on Wednesday when Vanity Fair unveiled its April cover featuring O'Rourke with photos taken by famous photographer Annie Leibovitz in his home town of El Paso. Kamala Harris of California, Elizabeth Warren of Massachusetts, Bernie Sanders of Vermont and Corey Booker of New Jersey, among others.
"I'm a capitalist", O'Rourke told reporters last month.
In 2012, he won against incumbent Democratic congressman Silvestre Reyes in a Latino-majority district, and was re-elected twice before giving up his seat to run against Cruz.