It wouldn’t need a separate app if, for instance, a standard QR payment format way created. If you just want a link to a website to pay, then naturally that would be less secure, but you could always put the URL below the QR code for redundancy (QR would only save time typing then).
The Democratic party doesn’t need to espouse any of that, it just needs to be less belligerent about opposing the issues since they’re issues where the party’s stance isn’t quite shared by the majority of the population. If you remove the stumbling blocks for voters, and instead focus attention on where the party shares its views with the majority of the US population, then wouldn’t it be natural that more of the center would shift your way?