Trump Campaign Lodges 105-Page Lawsuit In Pennsylvania. From the introduction:

While the bedrock of American elections has been transparency, almost every critical aspect of Pennsylvania’s November 3, 2020 General Election was effectively shrouded in secrecy. …

Allegheny and Philadelphia Counties alone received and processed 682,479 mail-in and absentee ballots without review by the political parties and candidates. These are unprecedented numbers in Pennsylvania’s elections history. …

As evidenced by numerous sworn statements, Defendants egregious misconduct has included ignoring legislative mandates concerning mail-in ballots – which amounted to over 2.6 million of the approximately 6.75 million votes in Pennsylvania — including the mandate that mail-in ballots be post-marked on or  before Election Day, and critically, preventing Plaintiff’s poll watchers from observing the receipt, review, opening, and tabulation of mail-in ballots. Those mail-in ballots are evaluated on an entirely parallel to those ballots cast in person. …

The right to vote includes not just the right to cast a ballot, but also the right to have it fairly counted if it is legally cast. The right to vote is infringed if a vote is cancelled or diluted by a fraudulent or illegal vote, including without limitation when a single person votes multiple times.

Note that the numbers of disputed votes are much larger than the Trump-Biden difference in the official count..