Sen. Elizabeth Warren joined Sen. Bernie Sanders on Tuesday in accusing former New York Mayor Michael Bloomberg of buying his way into the 2020 election, ahead of the ninth Democratic debate on Wednesday.

What she's saying: In a tweet, Warren wrote: "It’s a shame Mike Bloomberg can buy his way into the debate. But at least now primary voters curious about how each candidate will take on Donald Trump can get a live demonstration of how we each take on an egomaniac billionaire."

Sanders tore into Bloomberg at a Las Vegas campaign event last Saturday, saying the billionaire is trying to "buy the presidency" by spending millions of dollars on advertising.

Driving the news: Bloomberg qualified for Wednesday's debate after notching 19% in the latest NPR/PBS NewsHour/Marist poll.

By the numbers: Bloomberg's campaign is vastly outspending his top 2020 rivals on digital and network ad spending, pouring in about $318 million, per FiveThirtyEight.

His campaign announced a plan earlier this month to double ad spending, expected to reach $600 million for TV and digital ads alone.

Go deeper: The cost of going after Bloomberg