[schoen]

Maybe the phenomenon you describe would be weaker in U.S. politics if there were more political parties and less incentive for people to vote major-party. As it is, it seems like a lot of political journalism consists of different attempts at tea-leaf reading about which demographics were motivated to join which coalitions how, and whether the coalitions will shift, and how we would even know. I'm sure those phenomena also occur in other countries with a broader partisan landscape, but maybe they come with a smaller dose of speculation. :-)

[wasted_intel]

This unfortunately doesn't work well in a "first past the post" voting system, as a more general party will typically overpower a split opposition.

[schoen]

That's definitely a main factor that's tended to reduce the appeal of third parties.