The Senate failed to cap sky-high prices for insulin on sunday as part of the Democrats climate and health legislation.

A majority voted for it 57 senators but it wasnt enough under the Senates 60-vote rule for passage.

Yet just a few hours later, the Senate successfully protected subsidiaries of private equity companies from a new 15% corporate minimum tax rate included in the legislation.

It received the same number of votes as the insulin cap amendment, but this time the Senate rules required only a simple majority to pass it.

The difference in fate between the two votes, both of which received support from same-sized majorities, shows how the Senates arcane and frequently arbitrary rules often add to an already malapportioned legislative bodys bias toward powerful interests. People with diabetes looking for help to afford lifesaving medication need a supermajority, while a simple majority is just fine for private equity managers looking to protect their fruitful investments.

Most Democrats, up to a somewhat reluctant President Joe Biden , have been prepared to scrap or severely weaken the filibuster rule, the extra-constitutional provision requiring 60 votes to end debate in the Senate that has come to function as a supermajority requirement for almost all legislation. But Sens. Joe Manchin (D-W.Va.) and Kyrsten Sinema (D-Ariz.) have blocked any attempted reforms.

The combined effect of Senate rules is to create additional chokepoints for interest groups to exploit. Its not a coincidence that every major piece of economic legislation passed through the Senate during Bidens administration had the backing of the U.S. Chamber of Commerce, which represents Americas largest and most powerful businesses, until Sundays passage of the so-called Inflation Reduction Act.

The bill raises taxes on investors and large corporations, and spends the cash reducing the deficit and investing in clean energy and health care subsidies, while also giving Medicare the power to negotiate lower prices for prescription drugs. The House is expected to pass the legislation and send it to Biden later this week.

Passing the bill on a party-line vote in the 50-50 Senate meant Democrats were relying on whats called budget reconciliation. But reconciliation requires every provision of the bill to have a direct and substantial effect on the federal budget, making it useless for many social policies and any economic ones without a direct effect on federal taxation or spending.

The provision to cap insulin prices would have limited co-pays for insulin at $35 a month for people on private health insurance plans. But the Senates parliamentarian, an unelected official accountable only to members of the upper chamber, ruled it fell outside of whats allowed under reconciliation.

That meant the GOP could challenge it, and Democrats would need to round up 10 Republicans to keep it in the bill. Seven Republicans, all representing states with large swatches of rural poverty, joined Democrats: Susan Collins of Maine, Lisa Murkowski and Dan Sullivan of Alaska, John Kennedy and Bill Cassidy of Louisiana, Josh Hawley of Missouri and Cindy Hyde-Smith of Mississippi. But it wasnt enough.

Insulin prices have spiked in recent years, and Americans pay as much as 10 times more than what the drug costs in other economically developed countries. Four-fifths of diabetics who take insulin say the cost of the drug causes them financial hardship.

This wont just save money, it will save lives, Sen. Patty Murray (D-Wash.) said on the floor before the vote. This should not be a hard vote to cast.

The legislation still limits insulin co-pays to $35 a month for people who use Medicare, and Democrats have promised a stand-alone vote on legislation sponsored by Republican Susan Collins and Democrat Jeanne Shaheen (N.H.) to keep costs low. But unless three additional Republicans are willing to back the legislation, it will fail under the Senates 60-vote threshold.

Two of the worlds largest drug companies, Eli Lilly and Novo Nordisk, have been some of the biggest beneficiaries of rising insulin costs. Since the beginning of Democratic control of Congress in 2021, the two companies have spent massive sums lobbying against cost controls: Eli Lilly has spent $11.4 million, according to federal lobbying records, while Novo Nordisk has spent $5.8 million.