For better or worse, midterm elections are almost invariably referenda on the incumbent president. In four of the past eight midterm elections, the sitting president’s final preelection Gallup approval rating was 56 percent or higher. In those four midterms, incumbent party losses were minimal.

In the other four, presidential approval rating stood at 46 percent or lower. Those elections resulted in a seven-seat average net loss for the president’s party in the Senate, and 40 seats in the House. In the Senate, the specific seats up for reelection affect the outcome more than the national mood. And the map this year isn’t a pretty picture for Democrats. First, they must defend 26 seats, compared to just nine for the GOP. Second, five of those seats are from Republican states where Trump won by 19 points or more. Bottom line: A seven-seat net loss for Republicans in the Senate is a virtual impossibility. But just a two-seat net loss would cost them their majority.

It’s the House that is a more sensitive barometer of national political trends and where Republicans should be most worried. This past week’s Gallup poll put President Trump’s job approval at 40 percent, down from the previous week’s 42 percent, and 43 percent the week before that. Trump’s disapprovals are similarly ticking up, from 52 percent two weeks ago to 54 percent last week to 55 percent this week. This is certainly an improvement over where he stood a year ago, but down a bit from his approval ratings earlier this spring.

Eighty-five percent of Republicans approved of the president’s performance, compared to 35 percent of independents and 8 percent of Democrats. During the first two weeks of May, Trump enjoyed rare double-digit approval ratings among Democrats, the first time that’s happened in more than a year. It’s a decent bet that the flurry of positive news on the economy and fleeting progress on denuclearization on the Korean peninsula temporarily lifted some Democrats’ opinions of him.

CBS News and CNN also conducted live-telephone-interview polls during the first week of May. They found presidential approval ratings of 40 and 44 percent, respectively. The latest online SurveyMonkey poll showed Trump’s approval holding at 45 percent. Their political polling chief, Mark Blumenthal, noted that the president’s approval rating has been either 44 or 45 percent for the past eight weeks.

While the Gallup poll is a useful and consistent indicator to watch, because it’s repeated weekly, it does not routinely measure whether approval is strong or only moderate. Some network polls occasionally measure intensity, but we haven’t seen many lately. Gallup last did so in its May 14-20 survey, finding that 26 percent strongly approved of the job that Trump was doing and another 16 percent moderately approved, for an overall approval of 42 percent. Forty-one percent strongly disapproved with another 13 percent moderately disapproving. Gallup’s Jim Norman noted that respondents disapproving of Trump were more passionate in their feelings: Among those who disapprove there were three strongly disapproving for every one moderately disapproving, while among those who approved, the ratio of strong to moderate was 2-to-1.

The May 23 Gallup report noted that “the percentage of Americans who strongly disapprove of the job Trump is doing is one of the highest for any president in the history of the Gallup ‘strongly’ question, which has been asked 82 times at irregular intervals.” The only two presidents to eclipse his mark were George W. Bush, who had 44 percent strong disapproval in early 2006, as the war in Iraq was starting to grow more unpopular; and Richard Nixon, who hit 48 percent strong disapproval in February 1974, the year that he resigned.

The highest strong disapproval that President Clinton saw was 34 percent, while Barack Obama’s worst strong disapproval was 39 percent. In both cases, the intensity of strong disapproval preceded midterm election debacles.

Regrettably, there have been no nonpartisan, live-telephone-interview generic-congressional-ballot tests since early May, although one recent survey, conducted jointly for the Democratic SuperPAC Priorities USA by Garin-Hart-Yang Research Group and Global Strategies Group, shows Democrats with a 5-point advantage, 43 to 38 percent among all voters. Their lead swells to 10 points among those “most enthusiastic” (read: very high likelihood of turning out) voters.

Over the next 10 days, we should see a new round of national polls to help us get an updated sense of where the 2018 midterm elections stand from a macro-political view. A more micro-political, seat-by-seat analysis by The Cook Political Report looks like we could see a Democratic gain of anywhere from 20 to 40 seats. They need 23 to gain the speaker’s gavel back, while a 40-seat gain would create a Democratic majority somewhat more narrow than the one Republicans have today.

This story was originally published on nationaljournal.com on May 22, 2018