But as the first fund-raising deadline arrives at midnight on Sunday, Ms. Warren — who last year was widely considered a would-be front-runner — finds herself in a political vise. Her rivals on either ideological flank will raise substantially more money in the first quarter than she does, and her focus on policy has not yet translated in the polls.

Ms. Warren’s early troubles reflect the broader challenges confronting the vast Democratic field, all vying for money and attention as they seek to dethrone President Trump. Harvesting online donations does not come easily to noncelebrity candidates, and the party’s longstanding fascination with youthful charisma — along with its current, Trump-driven fixation on electability — can outweigh qualities like experience or policy expertise…

“If Warren says, ‘I can’t raise enough money, so my way to win is through an aggressive field operation because I have fired-up volunteers,’ well, Bernie and Beto can say, ‘O.K., well, we can do both,’” said Rufus Gifford, the finance director in former President Barack Obama’s re-election campaign.