Regular readers of this blog won’t be surprised to learn that Sasha Issenberg’s take on the midterm challenge for Democrats at TNR strikes me as the best single piece on the subject published to date. The Victory Lab author and intrepid student of the Obama campaign’s revolutionary approach to GOTV provides both analytical rigor and empirical support for the arguments I’ve been making for several years now about the persistence of two very different electorates–one that appears in presidential years, the other in non-presidential years–and their sudden synchronization with partisan preferences.

A decade ago, Obama memorably rebutted the trope that the United States could be neatly cleaved into a red and a blue America that pits coastal liberals against inland traditionalists. But in one very measurable and consequential sense, there are two Americas. There is the America that votes in presidential elections, which has helped Democrats win the popular vote in five out of the last six cycles and supports the view that Hillary Clinton can continue that streak should she run. Then there is the America that votes more regularly, casting ballots in both presidential and midterm years, which led to the Republican wave in 2010 and gives its party’s leaders reason to be so sanguine about their odds this time around.

There are about 127 million people in that first category, and among their number is the ascendant coalition—young and diverse, urban and mobile—that now gives Democrats a huge advantage in presidential races. But only 78 million of those people, or about 40 percent of the country’s voting-age population, belong to the group that goes to the polls every two years, and those regular voters carry a considerably more conservative cast. (The number of unregistered voters is almost as large.)

Over the past four years, the consequences of this schism have made themselves clear. A Democratic president is handed a progressive mandate by a convincing electoral-college victory. But he has his agenda unilaterally obstructed by a Republican House empowered by the right-leaning midterm electorate—an electorate that also disadvantages Democratic Senate candidates and sustains Republican governorships and state legislative majorities. Indeed, Democrats are facing an inverse of the four-decade span in the late twentieth century when the party controlled the House of Representatives and largely dominated the Senate but suffered through three two-term Republican presidencies. The bad news for Democrats is that the imbalance could take a generation to work itself out naturally. The good news is that, thanks to a newly nuanced understanding of the voting brain, they know exactly what it will take to fix it.

This last sunny prediction is based on Issenberg’s understanding of the theoretical underpinnings of the DSCC strategy for hanging onto the Senate this November by an intensive effort to use all the tools of the 2008 and 2012 presidential campaigns to boost turnout by what he calls “Unreliable Voters” (as opposed to high-midterm-turnout “Reflex Voters”). But he admits it’s a tricky business at best, based on a strategic gamble that investment in volunteer-based GOTV will more than offset a conceded Republican advantage in paid advertising.

In passing, Issenberg supplies an excellent brief history of theories about midterm elections, showing us that the prevailing “referendum” interpretation of midterms as purely and simply a predictably negative reaction to oversold presidential “mandates” is more hunch than science. And to my great delight, he also disses the idea of voter “enthusiasm” as the key to midterm turnout, while emphasizing that enthusiasm among the activists and volunteers needed for effective GOTV is indeed a very big deal.

Then there’s this insight about progressive agenda themes for 2014, which I’ve called potential “wedge issues:”

The real reason Democrats have embraced a progressive agenda has not been to energize their own base but to lure Reflex voters from the other side. Obama and his party’s candidates talk about the minimum wage in the hope that working-class whites skeptical of Democrats on other matters will become more ambivalent about voting Republican. Democrats’ renewed interest in women’s issues—including a defense of Planned Parenthood and embrace of equal-pay standards—is also designed with defections in mind. In 2012, the Obama campaign’s entire direct-mail program on women’s issues was targeted at reliable voters who leaned Republican: Field experiments in the first half of that year had showed that the messages were most persuasive among voters whose likelihood of voting for Obama previously sat between 20 and 40 percent.

But while Issenberg thinks Democrats have adopted precisely the right approach to mobilizing “Unreliable Voters” while seeking to “swing” “Reflect Voters,” the strategy will only work if the election is close, and that (this is my interpretation rather than his) probably depends on external factors like the economy and perhaps even perceptions of peril in foreign relations.

Democratic Senate campaigns will be designed to mobilize their way into contention, then persuade their way across the finish line. The risk is that November arrives and Democrats are so unpopular that the Unreliables they need to mobilize become too costly and the Reflex voters they need to persuade too far out of reach—“the tipping point where you can’t recover,” as [DSCC chief of staff] Cecil puts it.

All in all, I’d say reading Issenberg’s piece two or three times provides better guidance as to how the midterm campaign will develop than the next best twenty or thirty articles, not to mention the hundreds you will encounter that natter on self-confidently about the “referendum on Obamacare” or the “center-right nation” or the irresistible force of Americans for Prosperity ads. As he points out, the current alignment of the two parties with the parts of the electorate that do and don’t tend to vote in non-presidential contests isn’t eternal; for one thing, future cohorts of high-midterm-voting seniors are likely to be more progressively inclined than today’s. But for the immediate future, the Two Electorates is an abiding reality, and trying to understand either presidential or non-presidential cycles without comprehending that means stumbling around in the darkness.

Ed Kilgore

Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.