Two key parts to your hypo: 1. Google and party website: this can already be done and it is easily detected if a person is interested in a topic since other so

Two key parts to your hypo: 1. Google and party website: this can already be done and it is easily detected if a person is interested in a topic since other sources will broadcast the party position on a topic. 2. Party-centricity: depending on your locale, people vote for a person not a party. Party affiliation is often a proxy for how an elected person would behave but there are typically differences between party and people. Those differences are critical for voters who do not identify with a party. In the original hypothetical, candidates who differed from their party were better able to articulate that difference without broadcasting messages that alienated party stalwarts. I see this as a plus for democracy since people elect politicians whose behavior is more in line with voters’ interests. On the other hand, I can see from your hypothetical that segmenting messaging campaigns allows liars to hide lying a bit better, which is a clear negative.