The GOP plan would also reduce federal spending on Medicaid, which primarily serves the poor and needy seniors receiving long-term care.
So far, the bulk of the spending to defend the budget proposals drafted by Rep. Paul D. Ryan (R., Wis.) and strongly endorsed by House Republicans has come from 60 Plus, a conservative nonprofit group that has spent $800,000 in recent days.
"Our congressman, Allen West, voted to protect Medicare and keep it secure for future retirees," said one radio ad running in West's Florida district, one of the 39 districts targeted by 60 Plus.
Unlimited sums
The organization, which can solicit and spend unlimited sums because it is not part of a political party or a specific candidate's campaign operations, is not required to identify contributors.
It spent $7 million in the 2010 election cycle, backing Republican candidates on a range of conservative issues.
A variety of groups on the left are also up on the airwaves, some for the first time.
One Democratic-leaning independent group, the House Majority PAC, released a radio ad last week targeting freshman Rep. Sean Duffy (R., Wis.) for embracing the GOP budget.
"While Duffy's budget leaves the wealthy fat and happy, it puts the squeeze on Wisconsin families, and will end Medicare as we know it. That's right, end Medicare as we know it," the ad said.
The Ryan budget, the primary goal of which is to reduce the federal deficit, would give seniors a fixed amount of money to spend on private health insurance instead of paying for all covered medical expenses as the program does now.