As political scientist Nolan McCarty explains, "party sorting can account for the increased differences across partisans even if the distribution of...attitudes in the population remains unchanged or moves uniformly in one direction or the other."
According to McCarty, this explains the widening gap between the two parties, considering how pro-immigration viewpoints between the two surveys have increased by 35% since 1994.
[1] One school of thought led by Morris Fiorina[2] concludes most of the change comes from ideological partisan sorting, with polarization having little effect or being solely limited to political elites.
[4] Research by political scientists in 2012 found that people prefer to relocate to areas with copartisans, though it was unsure if it was a central or secondary factor.
[5] Research conducted in 2016 concluded that political compatibility is not a significant factor in deciding where to live.