They already did that - the Democrats are/were clearly not the same as the Republicans and that should have been enough (especially after we already got a preview of Trump's Republican party the first time around). They already ran strong enough campaigns and their candidates were already good enough. Most of them actually wanted the job because they believed in the mission of government, not because they personally benefited from ruining whatever office or authority they might be given.

The only thing the non-Republican voters had to do was show up, hold their nose over whatever bullshit short-coming their rep had (in comparison to "perfect" and whatever it is the Republicans offer to voters), and vote for whichever jerk had a D next to their name. There were only ever two options and U.S. citizens fucked up - through either silence (mostly) or blind support of whatever it is that's happening now.