WASHINGTON (AP) — With a new promise of $20 million to help defeat Donald Trump, billionaire Facebook co-founder Dustin Moskovitz becomes one of the top Democratic donors of the election

The Silicon Valley entrepreneur calls the Republican presidential candidate dangerous and divisive and says his appeal to Americans who feel left behind is "quite possibly a deliberate con."

By contrast, Moskovitz says, Democrats and their nominee, Hillary Clinton, are "running on a vision of optimism, pragmatism, inclusiveness and mutual benefit."

Moskovitz wrote about his planned contributions in a Thursday night posting on the website Medium titled "Compelled to Act." Until now, Moskowitz had made only one federal campaign contribution, $5,200 in 2013 to Democrat Sean Eldridge. The husband of another Facebook co-founder, Eldridge unsuccessfully ran for a New York congressional seat.

Half of the $20 million Moskovitz and his wife, Cari Tuna, are giving will go to the League of Conservation Voters and to a political action committee called For Our Future. The latter group is a get-out-the-vote effort in battleground states that is paid for primarily by labor unions and hedge fund billionaire Tom Steyer.

Moskovitz and Tuna also are giving directly to Clinton's campaign and to party committees helping Senate and congressional Democrats.

"As a nation, we need to figure out how to bring everyone with us, and we believe the Democratic platform currently is more aligned with ensuring that happens," he wrote.

"In comparison, Donald Trump's promises to this group are quite possibly a deliberate con, an attempt to rally energy and support without the ability or intention to deliver. His proposals are so implausible that the nation is forced to worry that his interest in the presidency might not even extend beyond winning a contest and promoting his personal brand."

Only Steyer has given more this year to Democrats, campaign finance records show. The Californian has put up almost $40 million so far, to promote environmental issues and help elect Clinton and other Democrats.