Millions of dollars are being poured into the fight over prescription drug costs — and not just from pharmaceutical companies and their allies. Consumer groups are making clear that they're not letting up on the issue, either.

Why it matters: Lowering prescription drug costs has been a top Democratic priority for years and is hugely popular among the public, a fact that both supporters and opponents of reform aren't taking lightly.

State of play: The path ahead for Democrats' major drug pricing bill — which includes a measure that would allow Medicare to negotiate prices — became even less clear earlier this month when 10 centrist House Democrats signaled their opposition to the bill in a letter to House Speaker Nancy Pelosi, as Politico reported.

• The House bill has always faced an even higher lift in the Senate, where all 50 Democrats would have to support it for any real hope of passage.
• But polling suggests that support for lowering drug prices is sky high across all political ideologies. In December, a KFF poll found that 89% of respondents said they support allowing the government to negotiate lower drug prices.

Driving the news: Multiple groups have announced seven-figure ad spends on drug pricing just this month.

• Yesterday, Patients for Affordable Drugs Now announced it's launching a seven-figure national campaign in support of the House bill in 42 House districts — including those of the members who signed the letter to Pelosi.
• The purpose of the multimillion-dollar campaign is "to make sure that we maintain momentum and that pharma’s lies and scare tactics don’t go unanswered," said David Mitchell, the group's founder.
• Earlier this month, Protect Our Care also launched a seven-figure campaign advocating for Medicare to be able to negotiate drug prices.

The other side: The American Action Network has announced it will spend at least $5 million opposing the House bill. And the pharmaceutical and health products industry is by far the top lobbying spender so far in 2021, as is usually the case, per the Center for Responsive Politics.

• “The left has long believed socialist price controls on prescription drugs would be a political winner. But now with unified control of Congress and a real chance to move it, we want to ensure voters see firsthand just how devastating their gambit really is," said Calvin Moore, communications director for AAN.

Between the lines: For most other issues, an unclear path forward paired with multiple competing legislative priorities wouldn't exactly be a recipe for success. But lowering drug prices is way more popular than most other issues.

• “I think the fact that drug pricing is such a popular issue in the electorate is one of the key factors that has helped keep it in play — and will keep it in play," Mitchell said. "There’s a big upside to doing something to lower drug prices, and there’s a big downside at the ballot box next fall to not doing something to lower drug prices."
• The policy also saves the federal government billions of dollars, which could help offset the cost of Democrats' other legislative priorities — a rare feature of popular policy measures.