Emotional arguments are pretty effective at convincing voters. Consider Obama’s “Hope,” W. J. Clinton’s “Man from Hope,” and Trump’s “Make America Great Again;” all effective emotional slogans that won over voters. Contrast this with Gore, McGovern, Romney, or H. R. Clinton’s campaigns that were more technocratic in their appeals.
What Democrats need to remember is that positive arguments are way more effective then negative ones, both in terms of winning votes and for setting the stage for future governance. While many people will rightly point to the negativity in the Trump campaign, what he was selling to his voters was the promise of a better tomorrow.
Rather than hoping that condemning Trump will lead people to the polls, Democrats need to sell an even better tomorrow to voters. Once they come around to this, they’ll be pretty effective as the Democratic party advocates many positions that, unlike their rivals, actually will create a better tomorrow for more voters. But first Democrats need to excise the hate.
What they need is a good mix of positive and negative emotions. There needs to be a positive vision of the future with a catchy slogan, combined with a series of ads featuring sympathetic victims of Trump's policies. Such people should be hard-working Real Americans™, i.e. disproportionately white - because swing voters are disproportionately white, and they don't want to trigger their implicit racist assumptions (e.g. blacks are on welfare). Most of Trump's horrible remarks and behaviors should be ignored, but amplify the ones where he implies he's better or smarter than everyday people, and use those in attack ads.
Swing voters, after all, are mostly low-information white voters, many of whom have plenty of implicit racism but almost none of whom are explicitly racist. That just is what it is. So their campaigning should be done with the knowledge that explicitly focusing on minority groups may turn off more white voters than it will increase turnout among minority voters.
That applies for the areas which are mostly white, particularly in the Midwest. Where the calculus appears to favor it - i.e. the number of minority voters who failed to vote in 2016 is higher than the swing to Trump among white voters - do the opposite and run plenty of targeted ads to minority groups.
Ideally the candidate will be either black or Hispanic him- or herself, but speak in the dominant General American accent. Obama showed that this is a very viable option. This seems to drive up turnout among minority voters without turning off white swing voters. It would actually not be surprising if this has a positive effect on white voters too: most white people are implicitly racist but like to think of themselves as not racist, and voting for a black or Hispanic person who talks and acts just like they do helps them to convince themselves that they're not racist. In particular, General American-speaking blacks are extremely heavily represented in TV commercials, which suggests to me that advertisers have found that this combination works really well.
So yeah, the best option would probably be Cory Booker portraying himself as an Everyman and focusing lots of attention on middle-class whites, with a sleek advertising campaign pushing positive feelings with a catchy slogan. Hey, it worked for Obama - why argue with success?