At first, Tom Steyer s late bid for the 2020 Democratic presidential nomination hardly made a ripple in Washington. The little-known billionaire threw his hat into the ring on July 9, months after a crowded lineup of other Democrats had hit the campaign trail running. He seemed to drop in out of nowhere.

But within a matter of weeks, 62-year-old Steyer was polling at an astonishing 7% in early caucus and primary states surpassing Kamala Harris, Pete Buttigieg, Beto ORourke and other big-name contenders. He even managed to secure a spot on Tuesdays Democratic debate stage, where hell debut his platform before an audience of millions.

Steyer told HuffPost he credits his success thus far to having a message that resonates with voters as important, true and different. But the environmental activist and liberal mega-donors stunning leap from relative obscurity to national prominence can also be traced to a controversial campaigning tactic borrowed from President Donald Trump s playbook: Funneling big money into voter data collection and targeted digital political ads.

Since vowing to allocate at least $100 million of his own $1.6 billion fortune to his campaign, Steyer has already vastly outspent all of his competitors, and its paying off. So far, much of his money more than $325,000 per day, according to The Wall Street Journal has gone to political ads, including many that urged people to donate a single dollar to his campaign, quickly enabling him to hit the required 130,000 individual-donor mark. Millions of dollars worth of Steyers ads have also targeted voters in key states such as Iowa, South Carolina and Nevada. He polled well enough in those three states to get into Tuesdays debate.

Beyond strategic geographic targeting, Steyer has invested heavily in data collection on millions of potential voters, his aides told The Atlantic , which has allowed him to target people with thousands of digital ad variations based on their individual interests.

Steyers team described his campaign strategy to HuffPost as being aggressive across all digital platforms, but critics have accused him of trying to buy his way onto the presidential ballot. And although he almost assuredly wont win the nomination, Steyers ability to so effectively customize his messaging for different audiences and to excel in certain states so late in the game by bombarding them with ads is alarming and illuminating: It reveals how little progress advertising giants have made in addressing the dangers of so-called micro-targeting in the wake of Russian ad-targeting campaigns during the 2016 election, and just how vulnerable American democracy remains to the influence of deep-pocketed actors.

Micro-targeting can affect election results and it can undermine democracy, said Michela Redoano, a targeted-advertising researcher and associate professor at the University of Warwick in England. Most voters arent even aware of micro-targeting. If you buy a newspaper of a certain political leaning, you know to expect bias. But if youre on social media, people arent necessarily expecting bias in the ads they see.