But unlike Mr. Obama, who ran in a year when the Iraq war was the single overriding policy issue in the Democratic race, Mr. O’Rourke is seeking the presidency at a moment his party is lurching left on issues across the board. He will be immediately under pressure to expand upon the sometimes-vague liberalism that has colored his public life.
Already, allies of Mr. Sanders in particular have questioned Mr. O’Rourke’s commitment to progressive priorities. (Mr. O’Rourke has declined to call himself a progressive, saying he was “not big on labels.”)
In 2016, he supported a centrist challenger to Nancy Pelosi to lead House Democrats. In 2018, he frustrated Texas activists by refusing to endorse Gina Ortiz Jones, a prized Democratic recruit for a House seat, because she was facing Mr. O’Rourke’s Republican friend, Representative Will Hurd, who eventually won by fewer than 1,000 votes.
Mr. O’Rourke should have little trouble pulling in enough money to get a presidential campaign off the ground, though it is possible that much of his fund-raising success in 2018 owed to his opponent, Mr. Cruz, whom liberals love to loathe.
Some in the party have questioned whether a Senate-race-losing candidate should even be running for president so soon. Senate Democrats aggressively lobbied him to take on Texas’s other Republican senator, John Cornyn, who is up for re-election next year, even dispatching senior party officials to El Paso to make the case.
In the months since his defeat, Mr. O’Rourke himself seemed to be casting about for answers, discussing a possible run with advisers but appearing genuinely conflicted — seeking clarity at one point by making a solo road trip to meet Americans in unrehearsed settings.
On Thursday, any lingering apprehension was well concealed.
“This is the moment,” he said, standing atop a coffeehouse counter in Burlington, hands flying, “for the leadership of the indispensable country.”
He left little doubt which leader he had in mind for the top job.