While Donald J. Trump and Kamala Harris enter into the final weeks of the presidential campaign, their lawyers are in a final push, too.

In recent weeks, the Republican National Committee and other Trump allies have ramped up an aggressive legal strategy, filing a barrage of election lawsuits across the swing states.

The cases are largely aimed at influencing the election rules before Election Day, although they may also lay the groundwork for Mr. Trump to try to overturn the results, as he did four years ago.

Democrats, meanwhile, are using the courts to push back against last-minute efforts by some election officials to change the way votes are counted and results are certified.

Mail ballots have been a target for Republicans since Democrats widely embraced the voting method in the 2020 election.

This cycle, Republicans have filed more than 20 lawsuits related to mail voting, often seeking to have thrown out any mail ballot that does not strictly meet all of the requirements in state law, and seeking to eliminate any opportunities for voters to fix an error with mail ballots.

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