Everyone who wants to know why President Obama’s health-care reform law isn’t very popular should watch the new Crossroads attack ad against Missouri Senator Claire McCaskill.

What’s wrong with the Patient Protection and Affordable Care Act (ACA)? First of all, Barack Obama: “Obamacare? More like Obama-Claire.” No question about it; one of the reasons the ACA wasn’t very popular in 2010 is because Obama wasn’t very popular, not the other way around.

But substantively? It’s all about generational conflict: “… cutting half a trillion in Medicare spending … the power to restrict seniors’ access to medical care.” Not a word about the individual mandate (which, to be sure, polls badly); not a word about anything, indeed, that has any effect at all on those who are not on Medicare.

Which is basically what happened in 2010, too. But it’s good to have a fresh example.

There is, of course, something deeply cynical about a Republican Party that blasts Obama and the Democrats for cutting Medicare in health-care reform at the very same time (sometimes in the same sentence!) as they attack Obama and the Democrats for refusing to cut (“reform”) Medicare. And then there’s the constant Republican carping about “Mediscare” — the idea that Democrats supposedly unfairly attack Medicare cuts, a complaint that hardly squares either with GOP support for the Medicare-cutting Paul Ryan budget or with the Medicare-based attacks on the ACA.

But the main takeaway from all of this is that Medicare is extremely popular, and Republicans know it — and that if in fact health-care reform hurt Democrats in 2010 or hurts Obama this time around, my bet is that it’s because of Medicare, not the mandate or “government takeovers” or “death panels” or, certainly, the core idea of exchanges plus subsidies.