What would American politics look like if MMD of 2-3 members were standard (esp for House)?

[インターネット掲示板ユーザー Punxsutawney Phil]

How would American politics look like if multi-member districts were the norm, with the rule being that the voter has as many votes as the district magnitude, minus one? And this was normal for many decades?
How would House elections function? What would the swing districts be?

[Skill and Chance]

This would mildly help Democrats in congress and state legislatures on a nationwide scale, though they would probably lose their supermajorities in CA, MD, MA, etc.