Amid threats of certification battles and mass voter challenges, Vice President Kamala Harris’s presidential campaign has assembled an expansive senior legal team that will oversee hundreds of lawyers and thousands of volunteers in a sprawling operation designed to be a bulwark against what Democrats expect to be an aggressive Republican effort to challenge voters, rules and, possibly, the results of the 2024 election.

The legal apparatus within the Harris campaign will oversee multiple aspects of the election program, including voter protection, recounts and general election litigation, and it is adding Marc Elias, one of the party’s top election lawyers, to focus on potential recounts.

The legal group is headed by Bob Bauer, who served as personal counsel to President Biden for years, and Dana Remus, the general counsel to the 2020 Biden campaign, and also includes Maury Riggan, the general counsel for the Harris campaign. Josh Hsu, formerly from the vice president’s office, will join the team, and Vanita Gupta, a former director of the Leadership Conference on Civil and Human Rights and a top Biden Justice Department official, is an informal adviser.

The campaign will also lean on the top lawyers at three prominent law firms — Seth Waxman, Donald Verrilli and John Devaney — to handle litigation, and deploy local counsel to eight battleground states and four other states of interest.

Mr. Elias, who has had tensions with Mr. Bauer and other Democratic lawyers in the past, will also bring lawyers from his growing firm, Elias Law Group. He has also previously worked for Ms. Harris, serving as general counsel for her primary campaign in 2020.

Ms. Remus said in a statement that the legal team had been working “uninterrupted over the last four years, building strategic plans in key states, adding more talent and capacity, and preparing for all possible scenarios.”