Billionaire presidential contender Mike Bloomberg did not qualify for Thursday night’s Democratic debate, but he had a different kind of megaphone in the form of a YouTube banner ad — one of the most expensive and widest-reaching digital advertising slots.

The Bloomberg campaign’s 24-hour ad campaign on YouTube, which boasts a reach of 2 billion viewers per month, was the latest effort by the wealthy candidate to flood the airwaves to make up for his late entrance in the presidential race.

The former New York mayor has already outspent his Democratic opponents on television and online. Since entering the race in late November, Bloomberg has spent at least $24 million on Google and Facebook, which includes their affiliated platforms YouTube and Instagram, respectively.

Bloomberg is the only Democratic candidate whose expenditures come close to President Trump, who has spent at least $31.6 million on Google and Facebook this year.

It remains to be seen whether the strategy will help Bloomberg increase his support among Democrats and the electorate as a whole. Following his launch last month, Bloomberg remained deeply unfavorable with voters nationwide, polls show.

Bloomberg is blanketing YouTube and Google search results with ads that have generated an estimated tens of millions of “impressions” — a measure of how many times users interacted with or were shown the ad.

Bloomberg has so far spent more than $18 million on Google — the same amount that the seven candidates who qualified for Thursday’s debate have spent combined on the platform all year, according to an analysis by Acronym, a Democratic nonprofit that focuses on digital ad spending and analysis.

“I think the strategy is to continue to boost his name-ID and surge in polling,” said Kyle Tharp, Acronym’s spokesman. “It’s an unprecedented amount of money in such a short period of time.”

Bloomberg is self-funding his campaign and said he will not accept campaign donations. The Democratic National Committee had set a polling and donor threshold for candidates to qualify for the debate.

On Friday, the DNC increased the number of donations necessary to qualify for the next debate, meaning Bloomberg again will not qualify. He told reporters on Friday that he is sticking to his policy of rejecting donations and abiding by the DNC’s donor threshold rules that bar him from debate.

“I want to get out my message to the extent I can. I’d be happy to compare myself to anybody else. But if they have rules that do not let me compete, then I just can’t,” Bloomberg said.

“I’m spending a lot of money, but my investment is to keep Donald Trump from being a president the next time,” he added. “Some of these candidates criticized me for spending a lot of money. I think you want me to spend less to get rid of Donald Trump? I didn’t think so. But you know, if they change the rules I’ll do it. And if they don’t, they don’t.”

Bloomberg’s online ad spending mirrors his television advertising strategy, running ads to gain name recognition in states that will hold primary elections on Super Tuesday.

The majority of his Facebook spending has targeted California, Texas and North Carolina, primarily with biographical spots and ads recruiting field organizers, data shows.

The 24-hour YouTube ad blitz that began on Thursday ran nationally on desktop and mobile home screens, and on YouTube TV in swing states, his campaign said. Experts say the typical price of an ad during high-traffic events on YouTube can reach up to $1 million for 24 hours. The campaign declined to disclose how much it spent on the banner ad.

“While Mike won’t be on the debate stage tonight because we are adhering to DNC rules, Mike still has a message he wants to share with the American people about leadership and how he spent his career bringing folks together to tackle big problems and fix them,” said campaign spokesman Michael Frazier.

Since entering the race, Bloomberg has spent more money than most other Democratic candidates spent all year attacking Trump directly, according to an analysis by Bully Pulpit Interactive, a Democratic digital consulting firm. And Bloomberg was the heaviest spender of campaign launch ads online, the analysis shows.

Bloomberg’s Facebook ads have focused on attacking Trump and highlighting the former New York mayor’s record on climate change and health care, as well as hiring field organizers, offering “great pay and benefits,” Facebook data shows.