… Structural changes in voters’ behavior are making it tougher for either party to amass, much less sustain, a comfortable Senate majority—except in rare circumstances. …
The big dynamic pointing toward precarious Senate majorities is the increasingly parliamentary nature of congressional elections. In the first decades after World War II, many voters routinely split their tickets, supporting one party’s presidential nominee and candidates from the other party in House and Senate races. But after peaking in the 1970s and 1980s, such split-ticket balloting has steadily declined in our polarized political era. CONT.
Ron Brownstein, National Journal