Democratic presidential candidates from left, Sen. Cory Booker, D-New Jersey; Rep. Tulsi Gabbard, D-Hawaii; Sen. Amy Klobuchar, D-Minnesota; South Bend, Indiana, Mayor Pete Buttigieg; Sen. Elizabeth Warren, D-Massachusetts; former Vice President Joe Biden; Sen. Bernie Sanders, I-Vermont; Sen. Kamala Harris, D-California; former technology executive Andrew Yang; and investor Tom Steyer participate in a Democratic presidential primary debate Nov. 20 in Atlanta. AP Photo: John Bazemore

Sullivan & Cromwell has a thing for Mayor Pete. Amy Klobuchar's fans work at white-shoe Wachtell, Lipton, Rosen & Katz, but also at plaintiffs powerhouse Kessler Topaz Meltzer & Check. Paul, Weiss, Rifkind, Wharton & Garrison is fueling Klobuchar's campaign too—and also helping keep Kamala Harris and Cory Booker in the race.

There are nearly 20 candidates competing to appear on the Democratic presidential ticket in 2020. And, as in every election cycle, most are getting by with a little help from their friends in Big Law.

The legal industry has donated millions to the Democratic contenders through Oct. 16, according to Federal Election Commission data compiled by the Center for Responsive Politics. But based on the Center's breakdown of the top 20 donors for each politician, the support is hardly even. Some candidates, such as front-runner Joe Biden, are notably reliant on campaign cash from donors connected to major law firms, which include attorneys, staff and political action committees, in addition to employees' immediate family members.

Other Democratic hopefuls—including Elizabeth Warren, Bernie Sanders and Andrew Yang—don't have any law firms listed among their top 20 funding sources.

Many large law firms, such as Kirkland & Ellis, Sullivan & Cromwell and Greenberg Traurig, are the source of sizable donations to multiple contenders, while Paul Weiss is the top source of contributions for three separate candidates.

Here are the contributions broken down for each of the leading democratic hopefuls:

Joe Biden

The former vice president has had ample support from Big Law affiliates, including $152,000 from Paul Weiss; $58,549 from Cozen O'Connor, $43,210 from Greenberg Traurig and $40,388 from Ballard Spahr. But his largest donor was National Law Journal 500-ranked plaintiffs firm Morgan & Morgan, whose affiliates gave Biden $421,040—nearly three times as much as Paul Weiss, his second-highest overall donor. Smaller firms such as Weitz & Luxenberg, which gave $99,695; and Baron &  Budd, which gave $37,055, were also on Biden's top 20 list. In all, lawyers and law firms were the second-highest industry from which Biden received donations, totaling $3,225,702.

Elizabeth Warren

No law firms were listed among the Massachusetts senator's top 20 donors. However, the legal industry is the fourth-highest donor to her campaign, to the tune of $1,066,935 in contributions.

Bernie Sanders

As with Warren, no law firms were among Vermont Sen. Bernie Sander's top donors. Ten other industries gave more to Sanders than lawyers and law firms did—the legal industry has donated $644,920.

Pete Buttigieg

Lawyers and law firms have donated $1,746,011 to Pete Buttigieg, making the legal industry the third-largest donor class to his campaign. But only one law firm, Sullivan & Cromwell, made the South Bend, Indiana, mayor's top 20 donor list; its affiliates have given $86,092.

Kamala Harris

Three large firms are among Kamala Harris's top donors. Number one was Paul Weiss, whose affiliates gave $184,477; Kirkland was her third-highest donor, with $140,671 in contributions; and DLA Piper—where her husband, Douglas Emhoff, is a partner—was her eighth-highest donor, with $95,000 in contributions. The legal industry was the second-largest supporter of the California senator and former California attorney general by sector, contributing $2,278,802.

Andrew Yang

Entrepreneur Andrew Yang, who was once an attorney at Davis, Polk & Wardwell, didn't have any law firms listed among his 20 largest donors. The legal industry has given a relatively small amount to his campaign—$123,297—and eight other industries have contributed more.

Amy Klobuchar

Behind Cory Booker, the Minnesota senator had the second-highest number of law firms in her top 20 donors. Her top three donors are Big Law firms: Paul Weiss affiliates have given $72,402, Kirkland affiliates have given $66,545, and Wachtell accounts for $60,625. Other donors include $46,800 from Kessler Topaz, $33,240 from Dorsey & Whitney, $24,054 from Alston & Bird. $23,595 from Jones Day, $23,500 from Lockridge Grindal Nauen and $23,201 from Debevoise & Plimpton. The legal industry was the second-highest donor industry for Klobuchar, and lawyers and law firms overall have given her $1,158,766.

Cory Booker

Half of Cory Booker's top 20 donors are law firms. Of those, five are Big Law firms and four are headquartered in the New Jersey senator's home state. His top overall donor is Paul Weiss, whose affiliates gave him $144,489, and his third-highest donor is Sullivan & Cromwell, whose affiliates gave him $75,936. Also in the top 10 are New Jersey-based Gibbons, whose affiliates gave $52,215; Kirkland, whose affiliates gave $44,970; Pennsylvania firm Kessler Topaz, whose affiliates gave $44,970; and New Jersey-based Lowenstein Sandler, whose affiliates gave $41,870. Booker also received donations from Simpson Thacher & Bartlett ($37,130); New Jersey-based Sills Cummins & Gross ($32,096); New Jersey-based Carella, Byrne, Cecchi, Olstein, Brody & Agnello ($31,705); and Greenberg Traurig ($30,706). The legal industry is Booker's top donating industry, and lawyers and law firms have given him $1,592,039.

Tulsi Gabbard

Tulsi Gabbard has received the smallest amount of donations from the legal industry of any other top candidate. No law firms were among her top 20 donors, and lawyers and law firms accounted for $89,937 in funds raised.