Ticket splitting (the practice of voting for both major parties) has been on the decline for a while. This has been measured in split-ticket House districts, which hit a near all-time low in 2012 and stayed under 1 in 10 districts in 2016. This picture shows by party, which I feel shows it by race in a way because nonwhites in general are overwhelmingly Democratic.
I feel that at least part of the party gap was driven by race because Pew data showed that about 55% of Democratic voters are white and 85% of Republican voters are white. Also, heavily white New England states had split tickets despite the Senate races not even being close for governor.
Are nonwhite Democratic voters in particular unlikely to engage in this practice? My analysis of precinct-level data suggests the answer is yes but I want to see a survey and/or in depth analysis.