The average price of a new cancer drug now exceeds $100,000 a year. The patient does not pay the entire tab, but someone who needs a prescription can still spend $25,000, not reimbursed by health insurance. That steep co-payment equals about half of what the typical U.S. household earns in a year.

It is not just new cancer therapies that bear stratospheric price tags. Last year Turing Pharmaceuticals, a New York City start-up, provoked widespread outrage after it bought a 62-year-old infectious disease drug called Daraprim and raised the price from $13.50 a pill to an astounding $750 a pill before agreeing to scale back the price slightly. Patients in the U.S. often pay much more than Europeans for older drugs—not just for new pharmaceuticals protected by patents. In the U.S., prescription drug spending increased 13.1 percent in 2014, the highest annual increase since 2003.

The president we elect in 2016 needs to bring these prices down. With the political primaries now at full tilt, sky-high prices at the pharmacy have drawn the attention of voters. Polls say that Democrats and Republicans want the government to take action on drug costs, but regulation-shy Republicans have more of a problem formulating coherent policy.

The leaders in the Democratic race—Hillary Clinton and Bernie Sanders—have set out detailed proposals with some ideas in common: both candidates want to empower Medicare to use its purchasing power to negotiate prices with drug companies to get the best deal. And both propose that patients should be able purchase lower-cost drugs from foreign pharmacies, an option currently denied them.

Republican candidates have mostly dodged the issue. During a primary debate in late October, retired neurosurgeon Ben Carson said, “Some people go overboard when it comes to trying to make profits” but then quickly added that more regulation is not the solution: “Government is not supposed to be in every aspect of our lives, and that's what has been the problem.”

The Republicans are making a strategic error if they do not take this issue more seriously. In an April poll, the Kaiser Family Foundation reported that Republican voters viewed outsize drug prices as a more pressing concern than getting rid of Obamacare. In an August follow-up, Kaiser found that three quarters of Republicans surveyed wanted Medicare involved in trying to obtain more reasonable prices from pharmaceutical companies.

The drug-pricing debate need not get bogged down in bickering about the merits of government regulation. Through long years of study, health care economists have mapped out policy options that are not inimical to market-based approaches to drug pricing. For example, Republican candidates could cite Switzerland as a model worthy of emulation: it first establishes a list of approved drugs and then sets a maximum price based on criteria such as R&D cost and effectiveness. But market forces—negotiations between a drug company and a private insurer—determine how much is charged up to the price ceiling.

At the very least, both Democrats and Republicans should prevail on drug companies for more transparency. Better data are needed to set better policy—and to evaluate claims by pharmaceutical companies that the billions spent to bring a new drug to market are justifiable. The candidates should also support laws or regulatory reforms at the national level that mirror bills that are making their way through legislatures in six states that require drug companies to provide more information about R&D and other expenditures.

If a just released drug can command the same price as a modest home in Oklahoma City, companies need to account openly for their costs and furnish some justification of the value that accrues to patients and insurers who foot the bill. And candidates from both parties need to pledge to make sure they do so.