Spending on U.S. digital political advertising in the current electoral cycle will likely top $1 billion for the first time, according to a new report.

Political campaigns and groups will spend $1.3 billion on online ads during the 2019-2020 election season, with more voters expected to donate to candidates in this year's presidential election, research firm eMarketer estimates.

Spending on digital political ads this election cycle amounts to more than three times the last presidential cycle, largely due to the large number of Democratic primary candidates, the research firm said. Those roughly two dozen candidates have spent millions to compile lists and acquire small donors, eMarketer noted.

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Beyond individual donations, billionaire candidates Michael Bloomberg and Tom Steyer have sunk large sums into their own campaigns and "prioritized digital ads in their ad mix," according to the report. The company also noted that President Donald Trump spent liberally on digital ads in revving up his campaign.

"Campaigns will spend the money they have, so to a large extent total political ad spending this year is dictated by the success of fundraising efforts — along with billionaires' willingness to spend their own money," eMarketer principal analyst Nicole Perrin said in a statement.

Facebook is pulling in roughly 59% of the money spent on digital political ads, which equates to $797 million, eMarketer projected. Google is a distant second, accounting for 18% of spending. Facebook continues to accept political advertising and has declined to impose as many restrictions as its competitors, including Google and Twitter.

Facebook said last month that it would not limit how political ads can be targeted to specific groups, as its Google did in November to fight misinformation. The social media company also has resisted calls to ban political ads outright, as Twitter did last October.

Spotify in late December said it would suspend political ads in early 2020, as the streaming music service could not ensure their accuracy.

That said, TV spending still rules, making up 66% of the $6.9 billion total that eMarketer projects will be spent on political ads.