It's an unpopular choice but I think the correct answer is actually 2008. You wouldn't see Democrats cheering the surveillance state, bombing Libya, saying banks are too big too fail or promote Heritage Foundation schemes instead of UHC under McCain as more-or-less Bush's third term. We get a more uncompromising Occupy Wall Street and antiwar movement, while the GOP crumbles under the weight of the Great Recession (which will be worse than OTL because of no stimulus).
I think people not picking 2008 is likely because it would require a greater timeline divergence than the other ones. And I think even if McCain somehow pulled it out, he likely would've still had a Democratic Congress.
For me, I can't pick 2008 because after living through Trump, I shudder at the thought of Palin being a heartbeat away from the Presidency.