With the “Come-One-Come-All” portion of the Democratic primary debate season complete, we are now about to enter the unpredictable Season of Momentum.

You can see momentum in a football game. It’s on the scoreboard. But momentum is a squishy thing in politics and political reporting. You can’t see it. You think you can feel it, or want to.

During these slow, somnolent summer weeks before the next round of debates in mid-September, political reporters will grow desperate for new narratives when nothing new is actually happening.

Candidates are saying the same yada-yada several times a day because about the 400th time they say it, audience members begin thinking, “Oh, I get it.”

News people can’t deliver the same report 400 times. They’d lose their company credit card and makeup person.

They need horse-race narratives, someone gaining, someone falling back going into the first turn and on and on. Which is, of course, ridiculous, like writing about the Kentucky Derby outcome 459 days before race time.

So far, this Democratic primary campaign is pretty boring stuff. Or scary, if you’re a taxpayer. A number of candidates — Robert Francis O’Rourke, Mayor Pete, for example — have enjoyed bursts of enthusiasm that evaporated.

Kamala Harris has tried a few positions to break out, unsuccessfully. As usual, Bernie Sanders is always shouting. Elizabeth Warren, who claimed minority status to get a cushy $400,000 teaching gig, is now against such crony corruption. Joe Biden was ahead early on. He still is. Yawn. Everyone is just waddling along.

Never fear. Soon, news stories and commentaries will begin appearing about momentum shifting to one candidate or away from another. Campaign communications directors love momentum if it involves their candidate gaining some, which can lead to more media coverage and more donors.

Media will use convenient documentation such as poll numbers, which are mere snapshots that have actually changed overnight. Or rally crowd sizes. Or man-in-the-street quotes. Or a veteran reporter’s intuition.

All of which can be entertaining and might by some fluke just be right. But it turns out, momentum it is not.

Bad news for us political writers. New research by Josh Clinton, a political science professor out of Vanderbilt University, proclaims political momentum to be basically a figment of our fervid imagination, at least during the 2016 cycle.

“Despite the (momentum) term being used so often,” Clinton says, “we wanted to see if voters were changing their votes to support winners.”

Clinton with graduate students Andrew Engelhardt and Marc Trussler combed through vast data from 325,000 interviews from December 2015 through the 2016 primaries. Clinton says:

If winning a primary created momentum among voters, we would expect to see a sizable fraction of voters changing their mind and supporting the winning candidate after each primary.

But in almost every case, the shifts we see are largely indistinguishable from the ordinary ebb and flow we observe in public opinion.

When a candidate won consecutive primaries, it was more due to states having similar electorates. And when a candidate’s winning percentage grew, it was no bandwagon, just that others had dropped out.

But what about these very important prime-time primary debates like the ones we’ve just endured? Clinton responds, “We again found no evidence that voters were reacting to debate performances.”

Now, you can take your own momentum on vacation and ignore politics with a clear conscience.