Yesterday, President Obama went to Florida and told seniors that Mitt Romney wants to end Medicare as we know it, and it appears that this argument (and some related ones) will be a central feature of the Obama campaign's message in the coming days. It's entirely possible, as Jonathan Chait has suggested, that all the Obama campaign's attacks on Romney's finances and record at Bain Capital are the first stage of a two-stage strategy that culminates with an attack on the Ryan budget. Since we'll be talking about this a lot soon, I thought it might be worthwhile to refresh our memories on what this is all about, particularly with regard to Medicare, and how it relates to the current campaign.