I'm not a political scientist, but it doesn't seem too far fetched? What OP seems to be saying is that it's easier to capture a small but strong follower base with focused effort, than a large (or any) follower base with diffuse effort. If the current social and political climate is any indication, people (at society level) genuinely don't seem to be receptive to efforts of unification and the betterment of mankind.
The agendas that are most successful are those which are laser focused to benefit particular groups, or even worse, to ensure that certain vilified groups have it worse. In the US, higher taxes are a very controversial topic, even if they would benefit the majority of the people. Even worse, some of the most ardent opposition is from the social class would most stands to benefit from liberal policies.
The whole game theoretic aspect of rational actors is out the window. Instead we have ever more isolated groups of people who don't care that they have it bad as long as their presumed opposition has it worse.
In light of all that, I'm actually inclined to agree with OP that a campaign that would benefit north of 50% of the population could easily be unpopular as a punchy opposition riles up the throngs of temporarily embarrassed millionaires to vote against their own interests.