Midterm years are all about two things: Referendum on the president (negative or positive) and voter enthusiasm. These two things are not unconnected.

There is a direct relationship between the president’s approval rating, which is normally low in the midterm year, and how badly the president’s party is shellacked at the voting booth.

There is a direct relationship between how enthusiastic voters are by party and how well a party does in the congressional races.

Right now, President Trump’s approval rating is rising. Going up. Improving. That means that his party’s candidates will not do too badly.

More importantly, though, is the enthusiasm numbers for voters. In a year in which there is a “wave” of one party’s or the others, that party’s voters have a relatively higher enthusiasm measure in polling. The absolute amount of enthusiasm is not the problem. The problem is the relative enthusiasm rate.

Right now, both parties have a high enthusiasm rate, and more importantly, they are the same. There is not statistical difference between how enthusiastic Republicans are vs. Democrats. They are both a) very enthusiastic and b) the same.

This pretty much cancels out any hope of an actual “blue wave.”

Consider earlier years. According to NBC/Wall Street Journal polling, voter enthusiasm for earlier years, and the outcome in congressional house races, break down as follows.

The larger difference in enthusiasm levels seem to have had an effect, and the absolute amount of enthusiasm of the winning party seems to have had an effect. Larger turnovers happened when both effects were strong.

This year, both parties have high enthusiasm, but the level of enthusiasm in both parties is high.

The only way that there could possibly be a blue wave this year, the only way for Democrats to take control of either house in Congress, or to produce any sort of anti-Trump mandate, is to have a large number of people who normally don’t vote show up and vote, or for a large percentage of people who normally vote for Republicans somehow change their minds. Young voters, suburban white women, somebody. Martians. Anybody.

And since those things never actually happen, people who normally don’t vote never actually vote, and people who normally vote one way only vote the other way in support of conservatives or Republicans and never progressives or Democrats, this election will be a disappointment.

We will have a midterm election during the first term of the demonstrably worse president in the 20th or 21st century in which Republicans gain seats in the Senate and Democrats pick up a few seats in the house, but not enough to matter.

Unless Democratic turnout rises to levels that have not been seen since the mid to late 19th century, when turnout was generally high in this country, this is what will happen: The Republicans will add between 1 and 3 seats to their majority in the Senate, and the Democrats will close the gap with the republicans by up to but not more than 20 seats, with the Republicans retaining the majority. And Trump and McConnell will be handed a mandate.

Then we are going to have to start asking ourselves what we are doing wrong.