Breitbart summarizes the key allegations as follows:

1. Observers were allegedly prevented from watching mail-in ballots being opened. Giuliani said that many mail-in ballots were opened without observers being able to check that they were properly signed, a key protection against fraud. Those votes, he said, were “null and void,” especially where the envelopes had been discarded, making recounts useless.

2. Allegedly unequal application of the law in Democratic counties. In Pennsylvania, whose state supreme court created new, relaxed voting rules before the election, Giuliani alleged that absentee voters in Democratic counties were allowed to “cure” defects in their ballots, while voters in Republican counties, which obeyed the state law as written, were not.

3. Voters allegedly arrived at the polls to discover other people had voted for them. Giuliani said that many provisional ballots cast in Pittsburgh were submitted by people who showed up to vote in person, only to be told that they had voted already. He alleged that Democrats had filled out absentee ballots for other people, hoping they would not show up.

4. Election officials were allegedly told not to look for defects in ballots, and to backdate ballots. Giuliani cited an affidavit from an official who swore she was told not to exclude absentee ballots for defects, and to backdate ballots so they would not appear to have been received after Election Day, to avoid a Supreme Court order to sequester those ballots.

5. Ballots casting votes for Joe Biden and no other candidates were allegedly run several times through machines. Giuliani said that there were 60 witnesses in Michigan who would attest to ballots being “produced” quickly and counted twice or thrice. He said that a minimum of 60,000 ballots, and a maximum of 100,000 ballots, were allegedly affected.

6. Absentee ballots were accepted in Wisconsin without being applied for first. Giuliani noted that Wisconsin state law was stricter regarding absentee ballots than most other states are, yet alleged that 60,000 absentee ballots were counted in the Milwaukee area, and 40,000 in the Madison area, without having been applied for properly by the voters who cast them.

7. There were allegedly “overvotes,” with some precincts allegedly recording more voters than residents, among other problems. Giuliani said there was an unusually large number of overvotes in precincts in Michigan and in Wisconsin, which he alleged was the reason that Republicans on the Wayne County Board of Canvassers had refused to certify the results there this week. He also alleged that there were some out-of-state voters in Georgia, and people who had cast votes twice there.

8. Voting machines and software are allegedly owned by companies with ties to the Venezuelan regime and to left-wing donor George Soros. Sidney Powell argued that U.S. votes were being counted overseas, and that Dominion voting machines and Smartmatic software were controlled by foreign interests, manipulating algorithms to change the results. Powell noted specifically that Smartmatic’s owners included two Venezuelan nationals, whom she alleged had ties to the regime of Hugo Chavez and Nicolas Maduro. The legal team alleged that there were statistical anomalies, such as huge batches of votes for Biden, that could not be explained except as manipulation — which, they alleged, happened in the wee hours of the morning as vote-counting had stalled. (The companies have disputed these allegations vigorously.)

9. The Constitution provides a process for electing a president if the vote is corrupted. Jenna Ellis argued that the media, had usurped the power to declare the winner of the election. She made the point, citing Federalist No. 68, that the constitutional process of selecting a president had procedural safeguards against corruption and foreign influence.Giuliani said that the campaign believed that enough votes were flawed — more than double the margins between Biden and Trump in key states — that the president had a path to victory.

"We will not be intimidated...We are going to clean this mess up now. President Trump won by a landslide. We are going to prove it. And we are going to reclaim the United States of America for the people who vote for freedom."—Sidney Powell