WASHINGTON (AP) — Joe Biden pulled in $81 million for his election effort in the month of May, a massive sum that shows the extent to which Democrats have unified behind the former vice president as he seeks to defeat Republican President Donald Trump.

The amount suggests that Biden won't have difficulty raising the cash needed to compete with Trump, even in the midst of a pandemic that has tanked markets, forced many out of work, or otherwise crimped peoples' ability to spend.

It also shows how far Biden has come from the Democratic primary, when his cash-strapped campaign was repeatedly out-raised by his rivals and lacked the money for TV advertising in key states.

"I understand what these dollars mean," Biden wrote in an email to supporters, announcing his cash haul on Monday. "When facing uncertainty and recession, you chose to back me. I will never forget that. And I promise that when I'm president, I won't let you down."

More than half of those who contributed to him last month were new donors, Biden's campaign said. The number of those who gave online has also tripled since February.

"I'm in awe of this sum of money," Biden wrote. "Just a few months ago, people were ready to write this campaign off. Now, we are making huge dents in Donald Trump's warchest. Every single dollar is going to make sure he is only a one-term president."

The $80.8 million Biden and the Democratic National Committee raised in May is his biggest cash take yet. Trump and the Republican National Committee have not yet released their numbers for the month.

Trump enjoys a massive cash-on-hand advantage and was sitting on over $250 million. But he has also spent big on national advertising that has yet to dent Biden's standing in public opinion polls.

In April, Trump and the Republican National Committee barely edged Biden, taking in $61.7 million, compared to the $60 million Biden raised with the DNC.

Biden's campaign also says it has benefited from a fundraising surge to progressive groups during the recent period of civil unrest.