He was re-elected to the House of Representatives twice, but declined to seek another term in 2018, choosing instead to challenge Sen. Cruz. He lost narrowly, 50.9 to 48.3 percent while setting a record for the number of votes cast for a Democrat in Texas.

O'Rourke, whose youthful looks and toothy smile have been compared to the Kennedys, tapped into his party's yearning for fresh faces in the age of Trump, raising a record $80 million in his Senate campaign, much of it from small donors. He's hoping to replicate that formula this time, and he raised an impressive $9.4 million in the 18 days after he joined the presidential race.

But O'Rourke has stumbled a bit in the early days of his presidential campaigns, angering women by saying is wife Amy did most the work raising their three young children and also for saying he was "born to be in it" in a Vanity Fair profile. He later expressed regret for the comments and suggested a woman would be on the ticket with him if he wins the nomination.

O'Rourke is considered somewhat moderate, at least by the standards of today's Democratic party, where presidential candidates are embracing policies like "Medicare for All" and higher taxes on the wealthy. According to a political scaling system known as DW-NOMINATE, O'Rourke's votes made him more conservative than 77 percent of the Democrats in Congress during his last term in Washington.

A recent poll from Quinnipiac University shows O'Rourke is still relatively unknown in California, trailing far behind former Vice President Joe Biden, Vermont Sen. Bernie Sanders and California Sen. Kamala Harris, who are the top preferences of Democrats and Democratic-leaning voters in the state. The California primary is March 3, 2020.