Not a whole lot, outside expanding federal power. Not that either party stands for much. They pay lip service to many of the same issues while being on board with other issues, although the politicians themselves can favor a wide variety of nonsense and then there are token issues that they use to sucker in voters. There are some differences on social issues where elected Democrats want to police everything under the sun while Republicans are like, "Yo, chill the fuck out."
Both Democrats and Republicans candidates will promote the same kinds of issues -- they'll both time about healthcare reform, they'll talk about prison reform, they'll talk about tax reform, they'll make some remarks about the economy, and so on. Then they have their separate approaches where Republicans try to shrink government (except the military) and Democrats try to government (often including the military). Of course, when a Democrat says "tax reform," it means hard-working Americans' taxes are going up (generally to pay more government employees or to pay people to not work), so there's one of your big differences.
They had had control of congress, senate, and the White House around when Obama took office. They literally could have done it then, just like they did with the ACA.
lolwut? First, most Democrats are too far to the left to be considered centrist in Sweden. Almost every candidate on the DNC's primary stage favored a wealth tax, something that even Sweden abolished and most of Europe got rid of. That's your baseline for candidates. At one point, the radicals were on the fringe for Democrats but -- like Republicans in the case of people like Ted Cruz who finished *second* in 2016 (although Jeb dropped out quickly) -- they've become more mainstream.
lol look at the traitor trying to go "both sides!"