It’s a truism of American politics so obvious that it’s treated as banal: Elections are decided by who shows up. Scholarly literature suggests that the electorate is highly stratified by race, age, and income—that is, the people who vote tend to be whiter, older, and wealthier than the American population as a whole, which skews the vote to the right. But there is also a less acknowledged “health bias” in turnout, meaning that people who are uninsured and in poor health less likely to vote. Though rarely discussed, this bias has important implications for policy. In a new report for the Century Foundation, I show that policy on many key issues is more right-wing than it would be with full participation across health and insurance status.

Academic research has found that the composition of the electorate has important implications for policy. For instance, there’s consistent evidence that income bias in turnout (the extent to which rich people vote at a higher rate than the poor) affects the provision of welfare; one study found that tighter voter registration deadlines exacerbate class bias in the electorate, enabling the passage of more punitive welfare eligibility laws. Studies also show that the enfranchisement of black voters is associated with reductions in black and white education gaps, as politicians began directing more spending to black localities. The enfranchisement of women is linked with increased spending on children and lower child mortality. In simpler terms: People tend to vote for their priorities, politicians listen to voters, and who votes is therefore vitally important.

Policies that influence turnout can therefore have the side effect of influencing policy in wide-ranging ways. Take voter pre-registration, which increases turnout among young people by allowing them to “pre-register” to vote when they get a driver’s license, even before they’re 18 (they’re added to the rolls when eligible). A recent study by political scientists John B. Holbein and D. Sunshine Hillygus found that pre-registration has a powerful impact on youth turnout, increasing it by somewhere between 2 to 8 percentage points. Another recent study shows why this matters: The passage of pre-registration legislation is associated with, for example, an increase in spending on higher education.

Scholars have also studied the health bias in turnout. Political scientist Julie Pacheco has documented that politicians are more responsive to healthier constituents than less-healthy constituents due to inequalities in political participation. In another study, she found that state-level bias in turnout by health status is associated with less generous Medicaid programs. My research shows that voters tend to be healthier than non-voters, and non-voters are less likely to be insured. According to the American National Election Studies (ANES) 2016 survey, the turnout rate among uninsured Americans was 34 percent, compared to a 63 percent turnout rate among those who were insured. Studies also show that people with disabilities turnout at lower rates. ANES data shows that the turnout rate among individuals with “excellent” or “very good” health is 64 percent; among those reporting “fair” or “poor” health, the turnout rate was 49 percent.

This is important because people who are in poor health or uninsured have different political preferences than those who are in good health or have insurance—unsurprisingly, the people who are suffering under the country’s existing healthcare system want to change it. Individuals in good health are more likely support government cuts, while individuals in poor health are more likely to support a more expansive role for government, with 41 percent of those in good health supporting cuts to government spending compared with 30 percent of those in fair or poor health. On the issue of health spending specifically, people in poor health are 8 percentage points more supportive of spending increases than people in excellent or very good health. Here’s a chart of what that looks like:

This bias has vital implications for efforts to expand Medicaid, which have largely been blocked by Republican politicians in states they control ever since the expansion was authorized by the Affordable Care Act in 2010. Expanding Medicaid is overwhelmingly popular, even in these red states. But those who support Medicaid may not be voicing that support at the ballot box: One study that examined the potential of Medicaid expansion in Alabama found that a stunning two-thirds of the beneficiaries of Medicaid expansion were not registered to vote. In many cases, this exclusion in racially tinged. The chart below, from my think tank Data for Progress, shows the black and white gap in support for Medicaid expansion by state. Research suggests that these racial disparities in public opinion can explain the differential implementation of the Medicaid expansion.

Numerous policies could alleviate these biases. For instance, states should make increased efforts to ensure that polling places are disability accessible, which is (unsurprisingly) proven to increase turnout among people with disabilities. States should also make efforts to expand automatic voter registration beyond DMVs. While 32 percent of individuals without a disability report registering at a DMV, only 25 percent of individuals with a disability do. This is increasingly becoming standard practice with automatic voter registration, and blue states like Rhode Island, Washington, and New Jersey that have implemented AVR have followed this practice.

One easy way to expand access the polls would be to include registration at the Affordable Care Act’s healthcare exchanges, something which sadly the Obama administration worked against. In addition, access to vote by mail and increasing disability access at polling places would also also reduce health bias in turnout.

As progressives wrestle with expanding ballot access and expanding healthcare access, it’s important to understand that both progressive fights are intimately intertwined. To create a truly inclusive healthcare system, we need a truly inclusive democracy.