Medicare is legal, as is SS.
The people paying for a fund that pays for old age pensions and healthcare is not a bribe. In fact most of the SS and Medicare money goes to people who are much less likely to vote. That's a terrible bribery scheme. It's clearly not bribery at all.
FDR passed all kinds of laws that Republicans like you tried to stop (and are trying again - you people never give up, because you always have budgets from your 1% masters). They have been challenged many times, and found Constitutional. The Courts upholding them after most of a century have been mostly appointed by Republicans, both presidents and Senates. Only a tiny percentage were appointed by FDR.
It's Republicans like you that keep the Supreme Court limited to 9 justices, because it's easier for you to corrupt it when it's far too small and overloaded with cases it must refuse. Despite the Republican lie you're peddling here, the Court never was and still is not limited to 9 justices. Its headcount up to Congress, which hasn't expanded it in going on a century, even as the country has multiplied its population, cranked up its count of states, and become far more litigious as people have far more power to damage each other.
But Republicans like you want Americans to starve and rot as we get old, subject to whatever predator can pay to carve them up, the way it was until SS and Medicare civilized the country. Lying about Courts and presidents is nothing to you, while you're savaging the people. But Americans still aren't the cannibals you're trying to trick us into becoming. Medicare and SS are the most effective and popular programmes among the people who create governments to protect our rights.