“It’s jaw-dropping the amount of time people spend on Facebook every day,” said Eric Wilson, a GOP digital strategist who served as digital director for Sen. Marco Rubio’s 2016 presidential campaign. “There’s so many voters on the platform, so many engaging on those [Facebook] platforms, so you have to be there.”

So far this year, Trump’s presidential campaign has spent nearly $6 million on Facebook advertising, according to data compiled by Bully Pulpit Interactive. He’s leading the pack of 2020 candidates in spending on the platform, despite accusing it of censoring conservative views and harboring a hatred for Republicans.

Former Vice President Joe Biden, who officially jumped into the 2020 race in April, has shelled out $1.4 million, and Sen. Elizabeth Warren, D-Mass., is not far behind, having spent $1.3 million since January while remaining a top critic of the Menlo Park, Calif.-based company and calling for its breakup on antitrust grounds.

Sen. Kamala Harris, D-Calif., has spent $1.2 million, while Sen. Bernie Sanders, I-Vt., paid $980,000.

“Facebook is the platform to go to because you’re getting really good targeting,” Wilson said. “They’re the best option at the lowest cost and reaching the most people.” The platform’s reach is extensive, too, with 243 million users a month just in the U.S. and Canada.

Brad Parscale, who served as digital director for Trump’s 2016 presidential run and is now running the 2020 campaign, said in a 2017 interview his team was making 50,000 to 60,000 Facebook ads on an average day, with varying language, colors, or wording.

“What it is is: What can make people react? What catches their attention?” he told “60 Minutes” then. “Remember, there’s so much noise on your phone, you know, or on your desktop. What is it that makes it go, ‘Poof! I’m gonna stop and look.’”

For the 2020 campaign, the reelection operation is aiming to collect contact information for between 40 million and 60 million people by Election Day, Parscale told Fox News in January. While it will keep using Facebook, Trump’s reelection effort is also going to tap into new technologies, he said.

“We try to harvest and bring people in to become direct contacts,” he told Fox News. “Cellphone numbers, e-mail addresses, things that we can have direct contact.”

Among the biggest ad expenses for the campaign was promoting Trump’s 73rd birthday, which was on Friday.

The operation doled out more than $900,000 on birthday-related ads since March 30, Bully Pulpit Interactive found, asking Facebook users to sign birthday cards for the president and first lady Melania Trump, who celebrated her 49th birthday in April. It’s a useful way to collect contact information from prospective supporters.

“It’s difficult for a candidate not to invest,” said Damon McCoy, an assistant professor of computer science and engineering at New York University. “At a minimum, it’s a good fundraising tool. I think it would be detrimental to a campaign at this point to not at least do some fundraising on the platform.”

While at this stage in the campaign the candidates are largely focused on expanding their email lists and soliciting donations, McCoy said the focus of the Facebook ads will shift as the primaries and general election draw near. Then, the ads will aim to recruit volunteers or get voters to the polls.

“There doesn’t seem to be any real drawback at this point,” McCoy said of advertising on Facebook. “At this point, you’re getting more money out of the system than you’re putting into it.”