The outcome of next week’s election depends on whether a “blue wave” will develop and erode some or much of the power Republicans hold nationally and in the states. For the past year we have seen evidence that a wave is developing. In fact, we’ve seen lots of evidence, like:

  • Unprecedented enthusiasm among Democrats who often sit out midterm elections
  • Off-the-charts candidate recruitment, especially among women
  • Massive Republican congressional retirements, far exceeding Democratic retirements
  • Outsized small-dollar fundraising that’s given Democrats a rare spending advantage over Republicans
  • A well-established pattern of Democrats way over-performing in special elections and in the 2017 general election
  • A persistent and sizable lead for Democrats in the House generic ballot
  • Expansion of the House map as the election draws near, with Republicans defending a lopsided number of competitive seats
  • Contraction of an exceedingly difficult Senate map, with non-competitive contests in several seats that would be close in a normal environment
  • Robust early vote figures, suggesting unusual levels of interest in the election

Something is clearly developing in the electorate—but wait. We have also seen interest in the election spike among Republicans, who for much of the year lagged well behind the enthusiasm exhibited by Democrats. And we know that previous wave elections have been defined by an uneven level of interest between the two sides. Essentially, one side is motivated, the other side is disengaged, and the motivated side sweeps contests they would ordinarily lose. That’s not going to happen this year.

Furthermore, Republicans have ways of defending against an onslaught of blue voters, and that’s where I think we should focus our attention in the waning days of the campaign. It’s a safe bet that there will be a blue wave next week. It’s less clear what that will mean.

Think of it this way: When a wave reaches the shoreline, what happens next depends on the topography of the beach. Low-lying barrier beaches might be cut apart by violent currents, whereas tall cliffs can survive a storm with minor erosion. Think of the three elections we’re holding next week—in the House, the Senate and the states—as taking place on different beaches, where the effects of a blue wave will depend on variations in the topography. Let’s call them House Beach, Senate Beach and State Beach.

House Beach meets the shore with a low, gentle slope composed of about fifteen Republican districts Democrats appear primed to win regardless of the magnitude of the wave. This gets them about two-thirds of the way to the 23 seats they need for a majority before the coastline becomes gerrymandered with boulders and rocks, rising steeply to heights that a normal wave could not breach. This region is composed of districts with significant numbers of Republicans, many of them likely voters, and it will be overcome only by a large wave fueled by unusually high Democratic turnout and help from independent swing voters. If such a wave materializes, Democrats will most certainly take the House. Beyond these heights are lowland valleys, scooped out by state legislatures to create the front range defenses. These districts—where Republicans outnumber Democrats by comfortable margins—would be sheltered from normal tides. But if a wave develops that’s massive enough to scale these heights it could be high enough to flood the valleys behind them, giving Democrats a substantial House majority.

Senate Beach looks entirely different. Imagine tall cliffs towering over the coast below. A quirk of the Senate map has left Democrats struggling to defend a host of senators in red states while giving them few opportunities to pick up seats. A wave big enough to wash in a House majority could break below the top of these cliffs, leaving Republicans in control of the Senate and perhaps with a chance to pad their narrow 51-49 majority. It will take a huge wave fueled by unlikely voters who are not being captured in opinion polls to propel the likes of Beto O’Rourke to victory in Texas. It’s improbable, but if it happens, the floodwaters won’t recede for a long time.

State Beach (which sounds like a real place) is different again. Portions are smooth and flat, others hilly, still others mountainous, depending on everything from the composition of the electorate to the strength of efforts to disenfranchise voters. It doesn’t look like there’s much in the Midwest to stop a wave, while Georgia has high, artificially fortified hills. The results will be similarly uneven absent a monumental wave.

Six days to go. Seven days to the start of the 2020 campaign.