Our new book is titled Divided We Stand: The 2020 Elections and American Politics. Among other things, it discusses state and congressional elections.
David Wasserman and Ally Flynn at Cook Political Report:
In 2020, Joe Biden became the first Democrat to carry a majority of congressional districts since Barack Obama in 2008. Biden carried 224 of 435 districts, up from Hillary Clinton's 205 districts in 2016 and Obama's 209 in 2012. A small factor in Biden's edge: between 2016 and 2020, courts in North Carolina and Pennsylvania ordered new maps that were less favorable to Republicans.
2020's results also lay bare the decline in split-ticket voting. The House is extremely well sorted out: just 16 of 435 districts "crossed over" to vote for presidential and House candidates of opposite parties, down from 35 in 2016 and 108 in 1996. Today, there are nine Republicans sitting in districts Biden carried, and seven Democrats in districts Trump carried. This beats 2012's record low of 26 districts.
In this new era of parliamentary voting patterns, House elections have increasingly become censuses counting blue and red voters in a given area rather than contests between two candidates of differing qualifications and backgrounds. And, the occupants of the few remaining "crossover" districts are at the top of each party's target lists in 2022, threatening to winnow their ranks further.