The claim that Republicans will "end the Medicare guarantee" has been a frequent refrain at the convention, perhaps in response to factchecker complaints about the incorrect charge last year that Republicans would "end Medicare." But this phrase is a bit odd since there is no actual "guarantee" for any program that can be changed by some future Congress.
The striking feature of Ryan's original Medicare plan was that when it's fully phased in, most seniors would not be able to afford healthcare. Ryan's updated plan is slightly different, but it retains the essential problem: The costs of healthcare would rise faster than the support seniors get to pay for healthcare, thereby making healthcare increasingly unaffordable.
Kessler should tell Democrats what the right way to talk about this is, because it's an important thing for voters to know.