Democrats decried dark money. Then they won with it in 2020.

Spurred by opposition to then-President Trump, donors and operatives allied with the Democratic Party embraced dark money with fresh zeal, pulling even with and, by some measures, surpassing Republicans in 2020 spending, according to a New York Times analysis of tax filings and other data.

The analysis shows that 15 of the most politically active nonprofit organizations that generally align with the Democratic Party spent more than $1.5 billion in 2020 — compared to roughly $900 million spent by a comparable sample of 15 of the most politically active groups aligned with the G.O.P.

The findings reveal the growth and ascendancy of a shadow political infrastructure that is reshaping American politics, as megadonors to these nonprofits take advantage of loose disclosure laws to make multimillion-dollar outlays in total secrecy. Some good-government activists worry that the exploding role of undisclosed cash threatens to accelerate the erosion of trust in the country’s political system.