Obama tried to get medicare drug negotiations into ACA but had to drop it to get the bill passed with dem majorities. Where was AARP?
AARP only cares about the status quo. A lot of their power comes from being seen as non-partisan by members (and protecting their interests). If they start acting partisan (towards the left) then they lose the ability to affect voters on the right. It also doesn't help that it's hard to explain to the average voter. They need easily digested sound bites.