Wouldn’t the conclusion of this article be rather that it is advantageous for a community to be less loyal to a political party? If say Republicans had a better chance of winning African American vote, that would likely affect their positions on number of issue, but for that to happen they have to have a realistic chance of wining more such votes for any votes they lose (which arguably currently they do not) — as a result African Americans would have more influence on both parties (currently democrats in turn take their votes for granted)
One correction on U.K. — the issue was not about “migration or communities of color” as article supposes. Actually quite the opposite — it was migration from other European countries into the areas that had few migrants before. That tells you that migration issue doesn’t have to be racial — it is primarily cultural.