2. Straight-ticket voting — Voters are splitting their tickets — voting for a Republican for one office and a Democrat for another — at lower rates than we’ve seen in decades. They’re just not making distinctions between parties’ presidential and congressional candidates like they used to. The decline of local news readership probably plays a role — after all, these outlets have traditionally provided an avenue for candidates to build a personal brand independent of their party’s.

In turn, that’s further narrowing the trading range of Senate and House seats that are truly up for grabs in November. Even a 53 percent Democratic district or 54 percent Republican district can now be considered a safe seat in most cases. Most races are no longer contests between two candidates with unique backgrounds and qualifications; more often they are censuses of how many Republicans or Democrats live in a given state or district.

3. Primaries have become the new general elections — The Cook Political Report currently rates just 37 of 435 House seats as competitive this fall, less than 9 percent of the House. As a result, primary elections have become tantamount to general elections in the vast majority of seats. Because primaries are held on many different dates, they tend to generate less national attention and attract disproportionate shares of hardcore, ideological party activists to the polls.

In 2014, only 14.6 percent of eligible voters participated in congressional primaries — a record low, according to the Center for the Study of the American Electorate. That means a tiny fraction of voters who are the most hardened partisans are essentially electing more than 90 percent of members of Congress. And these low-turnout primaries are often easy prey for ideological interest groups who demand purity.