WaPo:

Former president Donald Trump’s 2020 campaign commissioned an outside research firm in a bid to prove electoral-fraud claims but never released the findings because the firm disputed many of his theories and could not offer any proof that he was the rightful winner of the election, according to four people familiar with the matter.

The campaign paid researchers from Berkeley Research Group, the people said, to study 2020 election results in six states, looking for fraud and irregularities to highlight in public and in the courts. Among the areas examined were voter machine malfunctions, instances of dead people voting and any evidence that could help Trump show he won, the people said. None of the findings were presented to the public or in court.

About a dozen people at the firm worked on the report, including econometricians, who use statistics to model and predict outcomes, the people said. The work was carried out in the final weeks of 2020, before the Jan. 6 riot of Trump supporters at the U.S. Capitol.