Bernie Sanders has put the rest of the Democratic Party presidential primary candidates in a tough spot.

In the first six weeks of his campaign, Bernie has raised over $18 million. That money comes from more than half a million donors, with an average contribution of $20. He also has money left over from previous races, giving him about $28 million to work with.

It’s not that others in the crowded primary field can’t raise big money. Glitzy fundraisers and corporate schmoozing are second nature to Democrats. But the senator from Vermont has thrown them a curveball. By refusing to cozy up with titans of industry and relying instead on ordinary working people to fund both of his presidential campaigns, he’s turned Democrats’ most reliable fundraising strategies into a political liability.