What "legacy" would that be?
The ACA was a band-aid on a sucking chest wound. The US still ended up with by far the most expensive healthcare in the world, with some of the worst outcomes in the developed world. Obama was ruthlessly against any form of single payer, and made sure that that topic wasn't even discussed.
And what are his other legacies? Letting the Bush Administration off completely from the consequences of their crimes? His deliberate lies to start the Iraq War killed hundreds of thousands of people and more Americans than 9/11, and yet Obama chose to do... nothing!
The Libyan War? Syria? Yemen? The fact that Obama couldn't be bothered to bring either the Iraq or Afghanistan War to a close? American soldiers still die month after months in both of these places.
Oh, what about Obama's great love for the fossil fuel industry?
https://www.rollingstone.com/politics/politics-news/the-spill-the-scandal-and-the-president-193093/
Obama was our last hope. I cried with relief when he was elected, after the eight nightmarish Bush years. Now I see Obama as our last chance, squandered on mic drops and photo-ops. I can't even look at him.
