The electorate in midterm elections tends to be whiter and older than in presidential years. But — despite the focus of a lot of media coverage — that’s not the only reason Republicans are favored to win the Senate and keep the House in November. The GOP has gained ground relative to 2012 among registered voters, not just likely voters.

In the closing days of the 2012 election, Democrats led the generic congressional ballot by an average of 3.2 percentage points among registered voters, according to the final five polls that released registered voter numbers (CBS/New York Times, CNN/ORC, Gallup, United Technologies/National Journal and YouGov/Economist).

The generic ballot is a standard polling question that typically pits a generic Democrat against a generic Republican in a race for Congress. It’s one of the best indicators of the national political environment. Over the past month, the Democratic advantage among registered voters on the generic ballot is down to 0.5 points. That’s a gain of 2.7 points for Republicans.

In 2012, Republicans lost the national House vote (an aggregate of all House races) by 1.2 points. If the GOP picked up 2.7 points in 2014, it would win by 1.5 points. Historically, that margin would suggest a Republican gain of five to nine seats (there’s a large margin of error, plus or minus 12 seats, in that calculation).

All the talk about who votes and who doesn’t vote, however important, ignores the fact that Democrats are doing worse almost no matter how you slice the electorate. You can see this in another measure of the national mood; President Obama’s approval rating among all adults is down about 7 points since the election.

This isn’t surprising given that the president’s party almost always does worse in midterm elections. Still, it’s important to point out that what we are seeing on the generic ballot fits historical patterns. It’s not just an artifact of a changing electorate.