For both parties, the battle began before the election Tuesday, and before the coronavirus froze the 2020 campaign. Mr. Perez, the D.N.C. chairman, established a voter protection program last year, one of his “four categories” of party infrastructure, and has put “voter protection directors” on the ground in 17 states.
The D.N.C. is also involved in lawsuits across the country, ranging from ballot placement issues in Georgia, Arizona and Texas to a delay in changing election procedure in Kansas. In Arizona, the D.N.C. won a case overturning a law that prevented voters from delivering the ballots of their neighbors, a process derisively known as “ballot harvesting.”
Ballot collection is also a key part of litigation that the Democratic super PAC Priorities USA has brought in Michigan, where it is fighting restrictions on submitting ballots on behalf of others. Aneesa McMillan, a spokeswoman for the group’s voting initiative, said that the provision could take on added significance as more Americans become homebound and infirm.
Republicans were highly focused on stopping Democrats from loosening such restrictions, which they have portrayed as a Democratic ruse to inflate voting tallies. As Mr. Trump put it Wednesday night, “thousands gathered and they come in and dump the location and you lose elections.”
In New Mexico, the national party was assisting its local arm in suing to block a statewide postal ballot. And, on Wednesday, the Minnesota Republican Party chair, Jennifer Carnahan, indicated she would fight a proposal by Secretary of State Steve Simon, a Democrat, to move to expand postal balloting, calling it a “power play by Simon to steal the free and fair election process of our state and country.”
For their part, public health officials were urging Republicans to drop their resistance to measures that could protect the electorate.
The David Geffen School of Medicine at U.C.L.A. has joined with the school’s Voting Rights Project to call for “universal vote by mail.”