Democratic 2020 U.S. presidential candidate Pete Buttigieg, mayor of South Bend, Indiana.

The path to the 2020 Democratic presidential nomination may run through the caucus and primary states early next year, but the starting line is painted across the halls of Big Law in 2019.

Former Vice President Joe Biden announced his third presidential bid on Thursday before heading to a Philadelphia fundraiser the same evening. The event was held at the home of megadonors Rhonda and David Cohen, a former Ballard Spahr partner and a senior executive vice president of Comcast, respectively. Headliners of the event included congressmen, a governor, a mayor, a senator, and Steve Cozen, co-founder of Cozen O'Connor.

Cozen's attendance at the fundraiser, which ran attendees $2,800 a head, was not surprising. He is a longtime Democratic donor, including to some of Biden's potential 2020 competitors, such as Sen. Cory Booker of New Jersey.

Cozen's law firm is not quite ready to endorse #Joe2020, but that doesn't mean it hasn't embraced the candidate.

“We have lawyers who support both sides of the aisle, including those who have deep connections with several of the current Democratic candidates for president, and the firm will likely support those candidates,” said Michael Heller, Cozen O'Connor executive chairman and CEO, in a statement. “Joe Biden has been a long-time friend of lawyers at our firm and we would expect to support his candidacy as well, including hosting him at our offices.”

Sens. Cory Booker, D-New Jersey, and Kamala Harris, D-California.

Several others in the crowded Democratic field, or mulling whether to crowd it further, have been leaning on Big Law as well. Last month, New York City Mayor Bill de Blasio spent a weekend in South Carolina that included stumping on the 17th floor of Nelson Mullins Riley & Scarborough's offices in Columbia.

The campaign of Pete Buttigieg, the South Bend, Indiana, mayor, paid Jenner & Block close to $82,000 for legal consulting, and the presidential campaign of Sen. Elizabeth Warren of Massachusetts dropped $80,000 into the pockets of Perkins Coie for consulting, according to filings made public earlier this week.

Booker is one of seven Democratic lawmakers running for president who has reportedly sworn off contributions from lobbyists who register with the federal government, but lawyers at big firms are giving readily. Paul, Weiss, Rifkind, Wharton & Garrison employees gave Booker $134,750 in individual donations through the first quarter of 2019, according to the Center for Responsive Politics. Paul Weiss employees have also given more than $137,000 to Sen. Kamala Harris of California, $54,600 to Sen. Kirsten Gillibrand of New York, nearly $17,000 to Sen. Amy Klobuchar of Minnesota, and slightly more than $12,000 to Buttigieg.

Harris is a favorite of many Big Law firm lawyers, raking in more than $48,000 in aggregate individual donations from DLA Piper and more than $35,000 from Hueston Hennigan. Klobuchar's Big Law backers at Wachtell, Lipton, Rosen & Katz sent her $26,400, and Julian Castro, the former Housing and Urban Development secretary turned presidential candidate, took in $22,000 from Stris & Maher employees.

Wachtell was the biggest source of individual donations to Klobuchar out of any company or business in the Center for Responsive Politics roundup, while Paul Weiss was the largest single source of individual donations for both Booker and Harris.

Such donations could go a long way to lifting a Democratic candidate onto the presidential debate stage, given the national party's new rules. For the first time in the party's history, any candidate that gathers contributions from 65,000 unique donors and 200 unique donors across 20 states will be granted access to the nationally televised debate stage.

Seven Democrats look to have already qualified for the debate stage through donations alone, according to FiveThirtyEight: Buttigieg, Hawaii Rep. Tulsi Gabbard, Harris, former Texas Rep. Beto O'Rourke, Vermont Sen. Bernie Sanders, Warren, and businessman Andrew Yang.