With less than 200 days until the midterm elections, Democrats are generally thought to have a slight advantage in the fight for control of the House. That doesn’t mean they are going to prevail. The polls could be wrong, as all should understand by now, and there’s more than enough time for the national political environment to turn in favor of the Republicans. But these four indicators, for now, are consistent with a Democratic edge. Here’s what they are and what they’re telling us.
Generic Ballot: O.K. for Democrats, Worrying for Republicans
One of the best measures of the national political environment is the generic congressional ballot, a poll question asking voters whether they intend to support Democrats or Republicans in the next election.
The final generic ballot numbers typically perform well in approximating the House popular vote. Even this far ahead of an election, the generic ballot can do a decent job of predicting the final results. And Democrats can reasonably hope for their lead to grow, given the tendency of the measure to break toward the party out of power.
The Democrats’ lead on the generic ballot is around seven points, one of their weakest leads of the last year. At their peak, in December, Democrats led by 13 points, after the passage of the Republican tax cut bill.
Obviously, the larger the lead for the Democrats, the better their chances this November. But even a seven-point advantage is far from bad news for the party. In recent wave elections, the party out of power has won the House national popular vote by six to eight points. So there’s no contradiction between a seven-point Democratic edge and an extremely favorable national political environment.
It’s also consistent with most of the reporting on the state of specific Republican incumbents. A recent Politico article, for instance, described Republican troubles in safe districts like North Carolina’s 13th, North Carolina’s Ninth, Virginia’s Second, Virginia’s Fifth and Virginia’s Seventh.
By our estimates, those are exactly the sort of districts that should be vulnerable in a Democratic +7 political environment. Similarly, the distribution of Cook Political Report House Ratings are very similar to what we would expect for a D+7 environment.
Trump’s Approval Numbers: Good for Democrats
The fundamentals of this election cycle are clear: The party out of power usually dominates in midterm years when the president has an approval rating beneath 50 percent. These conditions have yielded a wave election in comparable situations since 1978.
If we take the last three decades of election results, a 41 percent approval rating, President Trump’s current rating, in a midterm year would suggest about an eight-point victory for the party out of power in the national House popular vote.
These fundamentals provide only a rough sense of what might happen in an election year. But in this case, they seem to line up with everything else.
Special Elections: Great for Democrats
In the special election in Arizona on Tuesday, the Republican, Debbie Lesko, won by just five points in a district that Donald J. Trump won by 21 points. There were no excuses for Republicans: The candidates were typical, the turnout was typical, and the G.O.P. fought hard for the district.
On average, Democrats have run 14 points ahead of a district’s partisanship (as measured by the last two presidential elections, compared with the national popular vote) in special elections for Republican-held districts so far this cycle. They’ve run more than 20 points ahead on three occasions — Kansas’ Fourth, Pennsylvania’s 18th and Arizona’s Eighth — and that doesn’t include Doug Jones’s victory in the Alabama Senate race.
These Democratic over-performances are a startling departure from the Obama years, when congressional election results polarized along national political lines.
Over the more than 1,000 special and general House elections in Democratic-held districts in the Obama era, there were only four elections when the Republicans ran 20 points ahead of the district’s lean in presidential elections. This cycle’s Democrats have pulled it off three times out of seven.
In a broader historical context, though, the Democratic over-performance is not quite as startling. It is still impressive, but the Democrats ran 20 points ahead of a Republican-held district’s presidential partisanship in 31 races combined in 2006 and 2008.
Over all, the Democratic performance in 2018 special congressional elections looks a lot like their showing in open districts in 2006, and well above the average from past wave elections in 1994, 2006, 2008 and 2010. On average, Democrats ran 14 points ahead of a district’s partisanship in open races in 2006 — exactly the same as the Democratic over-performance so far this cycle. The Democrats had a similar 10-point over-performance in 2008.
But 2006 is at least somewhat a cautionary tale for Democrats. Despite running 14 points ahead of presidential performance in the open seats, they flipped only 31 districts — a tally that would barely get the Democrats over the top this year (they need to flip 23).
Republicans held down their losses because their incumbents did pretty well. How well will incumbents fare in 2018? That’s one of the big unanswered questions heading into the heart of the election year. Since 2006, the value of incumbency has diminished. Instead, congressional elections have moved closer to aligning with presidential election results.
Specific District Factors: O.K. for G.O.P., but No Longer Great
At the beginning of the cycle, Republicans seemed to possess big structural edges: the advantages of incumbency, gerrymandering and geography. Combined, they appeared to give the party the ability to survive a wave election.
Those advantages still exist, and the Republican House majority could still survive a wave. But the G.OP.’s advantages are diminished. Here’s why:
Court rulings have weakened or undone Republican gerrymanders in Pennsylvania, Virginia, North Carolina and Florida.
An unusually large number of Republican incumbents have retired, in many cases well-established moderates with the best chance of riding out a wave election, like Dave Reichert in Washington State, Frank LoBiondo in New Jersey and Ileana Ros-Lehtinen in Florida.
Where Republicans are running for re-election, Democrats have generally succeeded in luring viable recruits backed by abundant fund-raising. The strong Democratic recruitment, in effect, tends to cut against the G.O.P.’s incumbency advantage.
Put it together, and the House Republican majority doesn’t look safe in today’s national political environment. As recently as late last year, you could credibly argue that Republicans would be solid favorites if the Democrats led on the generic ballot by seven points. The Republicans have managed to narrow the Democratic advantage to exactly that figure.