Candidates with the most individual donors Darker shades on the map indicate a greater share of estimated donors. 1. Sanders 1,395,000 1. Sanders 1,395,000 2. Warren 892,000 2. Warren 892,000 3. Buttigieg 741,000 3. Buttigieg 741,000 4. Biden 451,000 4. Biden 451,000 5. Yang 397,000 5. Yang 397,000 6. Klobuchar 227,000 6. Klobuchar 227,000

Note: Data is through Dec. 31.

Senator Bernie Sanders of Vermont received donations from an estimated 1.4 million people through the end of 2019 — far more than any other candidate in the Democratic primary race, according to fund-raising records filed with the Federal Election Commission. The map above shows his expansive donor base around the country, including in Iowa, whose caucuses will be held on Monday.

Mr. Sanders is powering his campaign with small donations from supporters across the United States, and he collected $96 million from donors in 2019 without holding a single high-dollar fund-raising event.

Our analysis of fund-raising records six months ago also showed his overwhelming strength in attracting donors around the country.

The map below — which includes the rest of the Democratic field without Mr. Sanders — provides a picture of where the other leading candidates are attracting donors.

Candidates with the most individual donors when Sanders is excluded Where Bernie Sanders is leading, the runner-up is shown. Darker shades on the map indicate a greater share of estimated donors. 1. Sanders 1,395,000 1. Sanders 1,395,000 2. Warren 892,000 2. Warren 892,000 3. Buttigieg 741,000 3. Buttigieg 741,000 4. Biden 451,000 4. Biden 451,000 5. Yang 397,000 5. Yang 397,000 6. Klobuchar 227,000 6. Klobuchar 227,000

Senator Elizabeth Warren of Massachusetts, who like Mr. Sanders is relying on grass-roots support, has the second largest number of donors in most states. While she, too, has found success with that strategy, she has not matched Mr. Sanders’s success.

Pete Buttigieg, the former mayor of South Bend, Ind., has the second largest number of donors in Iowa as well as in New Hampshire, which will hold the nation’s first primary on Feb. 11.

Sanders Leads in Early States

Looking at these numbers by state, Mr. Sanders is leading in all of the early states as well as all of the Super Tuesday states, except for Ms. Warren’s home state, Massachusetts, and Senator Amy Klobuchar’s home state, Minnesota.

How each candidate ranks in number of individual donors, by state

Sanders’s Donor Base Has Multiplied Over Time

This chart shows the estimated number of unique individuals who had given to each candidate over the course of 2019. Mr. Sanders’s huge base of donors is evident from the moment he joined the race last February.