(CNN) Advertising spending in the 2020 presidential race just barreled past the $1 billion mark, driven by Michael Bloomberg's relentless rounds of commercials promoting himself as the alternative to President Donald Trump.

Bloomberg, who is seeking the Democratic presidential nomination, accounts for more than half of all the spending, as he has plowed more than $501 million into television, radio and digital advertising since entering the race four months ago, according to data from Kantar Media's Campaign Media Analysis Group. That eclipses the $306.6 million President Barack Obama spent on advertising during the full two-year cycle leading up to the 2012 election.

"It's just an astonishing number of ads," said Erika Franklin Fowler, who co-directs the Wesleyan Media Project, which tracks political advertising. "We've never seen anything like this before -- not just the scale but in such a short window."

"Citizens always say they get sick of the presidential election by Election Day," she added. "But they can't escape it now, and it's just February."

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