The following article by Ruy Teixeira, author of The Optimistic Leftist and other works of political analysis, is cross-posted from his blog:

There is nothing more important than the overall political environment for the magnitude of Democratic gains in 2018. The poorer that environment is for Republicans, the better the Democrats will do in any given race with any given candidate. And there is nothing more important to that environment than President Trump’s approval ratings which, as those who pay at least some attention to politics know, have generally been dismal at the national level.

But the 2018 races are run not nationally but in the individual states, so it is important to have a sense of how Trump is viewed in individual states to assess Democratic prospects. That is why the state approval ratings just released by Gallup are so useful, because they provide an approval rating for Trump in all 50 states. (The ratings are average ratings from 2017; Trump’s overall approval rating today appear to be slightly higher–a point or two–than its 2017 average, so the Gallup data cited here may be slightly underestimating his current state approval ratings).

The state ratings are particularly interesting in light of where the real battles of 2018 are likely to be fought. As Philip Bump has noted, 64 competitive House seats held by Republicans are in states where Trump’s approval rating is under 50 percent; 60 of these seats are in states where his rating is below 45 percent and 34 are in states where his rating dips below 40 percent.

One way to get a sense of just how much the political environment in a given state has shifted since Trump’s election is to compare Trump’s margin in 2016 with his net approval rating (approval minus disapproval) from the Gallup data. The results are rather striking when we look at states with key races.

The states with the largest number of competitive House seats held by Republicans are: California (8); Pennsylvania (6); New York (5); New Jersey (4); Virginia (4); Illinois (4) and Ohio (4). Trump’s average approval rating in these states is 36 percent (low of 29 percent in California and high of 45 percent in Ohio). And on average Trump’s net approval rating in these states is 12 points worse than the margin he attained in these states in the 2016 election. For example, Trump carried Ohio by 8 points in 2016; his net approval rating in 2017 was -5. Interestingly, the only state where the shift against Trump was not in double digits was California. But here his margin in 2016 was already -30, so he slipped to “only” -36 in net approval rating.

Drilling down a little bit farther, the same patterns can be found in most states with competitive Senate, governor’s and/or state legislature elections. In Arizona, where Democrats are targeting Jeff Flake’s open Senate, as well as seeking to make big gains in the state House and Senate, Trump’s net approval is now -12, a 16 point shift compared to his 2016 margin. In Florida, where the Democrats are defending a Senate seat and targeting Republican governor Rick Scott and the state Senate, Trump is also at -12, 13 points worse than his 2016 showing. In Iowa, where the Democrats are after the governorship and serious gains in the state House and Senate, Trump’s net approval is -9, 18 points worse than his victory margin in the state in 2016. In Nevada, where Democrats have good chances to flip Dean Heller’s Senate seat and the governor’s mansion, Trump is at -11, 13 points worse than 2016. Even in North Dakota and West Virginia, two states with Democratic-held Senate seats where Trump has (in relative terms) sky-high net approval ratings of 18 and 26 points, respectively, these ratings still trail Trump’s 2016 election margins by 16 points.

Most astonishingly, in Texas where the Democrats are after three House seats and have an outside shot at Ted Cruz’ Senate seat, Trump’s net approval is at -15, a stunning 24 point decline from Trump’s victory margin in 2016. But a word of caution here. Gallup’s net approval ratings are among all adults, a group that tends to be pro-Democratic relative to the likely or actual voting pool and this difference, as Harry Enten has pointed out, is particularly large in Texas. So don’t break out the champagne toasts for blue Texas quite yet.

Still, all in all, favorable data for Democratic prospects in the most important states in 2018. I shall have more to say in the future about the demographics of specific states and Congressional Districts and how this may play into the political trends summarized in this piece