Our most recent book is titled Divided We Stand: The 2020 Elections and American Politics. Among other things, it discusses state and congressional elections.
Grover Cleveland in 1884 was the last newly-elected Democratic President to take office without Democrats also controlling the Senate. (Why this matters: There’s a decent chance Kamala Harris wins the White House while Republicans take the Senate, setting up confirmation crises & showdowns over debt ceiling, taxes & regulation.)
The party winning the White House has gained 15 seats in the House over the past century, on average. (Why this matters: With a current GOP margin of just four, the party that wins the White House in 2024 probably also takes the House).