Atlanta (CNN) Malinda Frevert will forever remember the day after Hillary Clinton's early morning speech conceding the presidential race to Donald Trump as "Surprise Thursday."

It was then, 36 hours after Trump's victory in November -- a day filled with despair and disbelief for millions of Democrats -- that groups like the liberal advocacy group Emily's List, where Frevert works, experienced an unexpected tidal wave of support. By the end of November, Emily's List had doubled its number of monthly donors.

"That's when we realized that something was probably happening and we needed to get ready," said Frevert, who handles online strategy at Emily's List.

Dozens of other liberal groups experienced a spike in interest immediately after the election. By January, membership at the ACLU skyrocketed to 1.6 million from just 400,000 on Election Day. Planned Parenthood took in more than 300,0000 individual donations. United We Dream, an immigrant rights group, saw its membership spike to half a million people.

The rush of enthusiasm took many by surprise.

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