Democratic presidential candidate Pete Buttigieg, the mayor of South Bend, Ind., proposed more than doubling Social Security’s payroll-tax cap — and he’s just the latest to do so.

Mayor Pete, as he’s often called, said he’d like to increase the cap of income eligible for payroll taxes from what it is now at $132,900 to about $250,000, while speaking at an AARP Forum in Iowa. “I have a very personal stake in making sure that Social Security and Medicare are there when you retire and when I retire, and if you look at the numbers, that won’t happen without some adjustments,” he said.

Other Democrats have suggested similar strategies. Fellow Democratic presidential candidate Sen. Bernie Sanders, the independent from Vermont, proposed subjecting anyone with income over $250,000 to the payroll tax, which would create a gap between the current tax cap and the new one. That gap would narrow over time as the cap naturally lifted every year. (The Social Security Administration follows the national average wage index to determine if and when the cap is raised.)

See: This hybrid Social Security pan could help more people save enough for retirement

Voters are watching out for plans to fix Social Security, especially given its struggles. The trust funds that support the program are at risk of depletion by 2035, and if that happens, retirees will receive only 80% of the benefits they’re owed. Although it’s unlikely Congress will let that occur, legislators are currently weighing their options to fix the program, such as higher taxes, a raised cap or an increase of the age at which one is eligible to claim benefits. The federal government is also looking into other ways to bolster retirement security.

To some Americans, Social Security is a lifeline. The benefit makes up a majority of cash income for 61% of elderly beneficiaries, and a third rely on it for 90% or more of their income, according to the Center on Budget and Policy Priorities. The average monthly retirement benefit from Social Security was $1,423 in June.

Older Americans are also a powerful voting demographic. People over 50 made up more than half of the electorate in the 2016 election, and older voters usually figure prominently in midterm elections, according to the National Committee to Preserve Social Security & Medicare.

The payroll tax amounts to 12.4% of a worker’s salary, but that percentage is split between the employer and employee evenly, so that each is contributing 6.2% (except for those who are self-employed). Workers with higher wages, however, stop paying into Social Security after meeting the cap — for many top earners, that happens around mid-February. Comparatively, someone earning $50,000 would pay taxes for Social Security until Dec. 31, according to the Center for Economic and Policy Research.

Also see: One reason lawmakers are hesitant to fix Social Security: the millennials

The Social Security 2100 Act, proposed by Rep. John Larson, a Democrat from Connecticut and chairman of the House Ways and Means Subcommittee on Social Security, along with Democratic Sens. Richard Blumenthal of Connecticut and Chris van Hollen of Maryland, would also raise the payroll tax, but to $400,000, as well as raise the combined payroll tax of 12.4% by 0.1% every year until reaching 14.8% in 2043. The cap would eventually be phased out altogether.

Some critics argue the cap is unfair to lower-income workers, who would be paying in more of their earnings per year than their higher-earner counterparts. Someone earning $30,000 in 2018 paid $1,860 in Social Security, or 6.2% of his salary (for his part of the payroll tax), compared with someone earning $200,000 that year who paid $7,961, or about 4%, of her earnings, according to a Congressional Research Service report published in October.

Supporters, meanwhile, say the current structure benefits a small group of high-earning workers, especially given widening income inequality and the fact that the 6% of individuals who earn more than the cap have had a higher percentage of their income escape taxation (from 12% to 17% since 1991).