In a previous post I suggested that the greatest threat to a Blue Wave this fall was sky high Republican turnout on behalf of a president with historically low approval ratings. Trump’s campaign strategy is to gin up his base by stoking division, including (as Paul Ryan has observed) straight-up trolling his perceived enemies. Thus far, his base is sticking with him as measured by his “own party” approval ratings. He is also able to sway a huge swath of Republican primary voters.

But of course the Trump onslaught can’t help but rile up his opponents as well. What reasons do we have for believing that a Blue Wave will crest on Election Day?

First, a brief aside to consider several views of what a ‘wave election’ is. Nate Cohn tweets:

I'm getting reluctant to use the word 'wave.' I feel like a lot of readers now associate it with these wild special election results, 15 pt dem swings, etc. rather than how I mean it–an election like 94/06/10.

— Nate Cohn (@Nate_Cohn) June 6, 2018

Amy Walter at the Cook Political Report, looking at the elections Cohn references – 1994, 2006, and 2010, provides a bar graph illustrating the number of seats needed by the out-party in each case plus the number of additional seats they actually won:

(Click for link at Cook Political Report and scroll down to view larger image.)

“By this metric,” she writes, “a gain of 35 seats by the Democrats should be considered a wave.”

Alexi McCammond at Axios points to a report by Ballotpedia, which begins with this definition: “We define wave elections as the 20 percent of elections where the president’s party lost the most seats during the last 100 years (50 election cycles).” Based on this criterion, Democrats would need to win 48 House seats for it to constitute a wave.

The bottom line, of course, isn’t whether the Democratic margin of victory hits a designated historical benchmark – though the political impact will be amplified as the margin of victory increases – it’s whether or not the Democrats win working majority in the House. At this stage, we don’t know, but if it happens, what will drive that victory?

“Reports from journalists and academics describe grassroots organizational activity by left-of-center citizens and groups that is unequalled since Barack Obama’s first presidential campaign, and disproportionate political engagement among women that may have been last matched during the push for the Equal Rights Amendment four decades ago,” writes David Hopkins at Honest Graft, who believes this is the underreported story of 2018, receiving only “a small fraction of the media coverage that was directed to the Tea Party movement in advance of the Republican victories of 2010.”

Hopkins argues that because the media loves conflict and – unlike the Tea Party, which aggressively challenged the Republican establishment – the grassroots movement opposing Trump hasn’t fractured the Democratic Party, created anti-Washington fervor, or given rise to ideological purity.

“We are left, instead, with a picture of millions of Americans arrayed from the political left to the center, disproportionately well-educated, suburban, and professional, who are simultaneously captivated and repulsed by the day-to-day behavior of Donald Trump.”

Theda Skocpal, a scholar who studied the Tea Party and has looked more recently at the opposition to Trump, notes that while activists from both groups sound surprisingly similar (“I used to vote. Now I realize my country could be lost, and I have to do more.”), the resistance to Trump is a center-left phenomenon led overwhelmingly by women. Skopal estimates that 70% of Indivisible participants, for instance, and most of its leaders, are women.

“These are middle-class women’s networks, with some men in them. They turned around public opinion on the Affordable Care Act. They were behind Conor Lamb’s victory, along with the unions. They’re everywhere, and they have made a real difference. They’re likely to be the key to congressional victories, if they happen.”

Tea Party activists were clustered on the ideological far right and infused with anti-establishment fervor. The Resistance looks different. She notes that it is not being driven by Bernie Sanders’ followers, nor the left-most stalwarts in the Democratic Party. Instead, they are as likely to occupy the middle of the road as the far left.

“They’re not likely to be highly ideological. They care about good government, health care, education, decency toward immigrants and refugees. A lot of them got involved through church networks…..

A lot of them are progressive, but they’re also pragmatic. They don’t insist on the leftmost candidate. They’ll get behind any reasonable Democrat.”

Will the anti-Trump movement push Democrats to the House majority in 2018? There are powerful obstacles to overcome. The most prominent, as George Packer puts it: “Democrats have a habit of forgetting to vote between Presidential elections.” And the demographic groups that boast the highest level of support for Democrats – such as young people, black and Latino communities, and working class folks – are the most likely to forget.

At this stage, though, the wind is at the Democrats’ backs. A study released at the beginning of this week, revealed a surge of Democratic enthusiasm, as measured by turnout in 2018 primary elections: up 84% compared with 2014. In comparison, Republican turnout is up only 14% relative to 2014.

But the bottom line is that votes cast, not increased turnout, will carry the day on November 6. And in many of the House districts that Democrats need to flip, Republicans outnumber Democrats. Plus, Republicans are simply more reliable voters.

Consider: among the most talked about House seats that Democrats are targeting nationally are a number of California districts, seven of which have been on the Democrats’ Red to Blue wish list for more than a year. They are: CD 10 (Jeff Denham); CD 21 (David Valadao); CD 25 (Steve Knight); CD 39 (Ed Royce – retiring); CD 45 (Mimi Walters); CD 48 (Dana Rohrabacher); and CD 49 (Darrell Issa – Retiring).

In six out of these seven districts, Republicans on the June 2018 primary ballot received more votes than Democratic candidates did. The only exception was CD 49, where 92,837 votes were cast for Democrats and 89,839 votes for Republicans. Representative Issa, alone among the Republican Congressmen from these seven districts, narrowly avoided defeat in 2016. The Cook Political Report rated (as of August 9) CD 49 as ‘Lean Democratic,’ though there is a slight Republican registration edge, with a Cook Partisan Voter Index (PVI) rating of ‘R+1.’

But, while Republicans turnout more reliably, more Democrats get out to vote for general elections than for primaries. With a ballot for California’s Governor and the U.S. Senate in November, Democratic turnout will dwarf what we saw in June. So Democrats can expect to be highly competitive, if not quite favored. Cook rated four of these races ‘Republican Toss Up’: CDs 10, 25, and 39, which all have a PVI rating of ‘Even,’ along with CD 48, which has a PVI of ‘R+4.’ Cook rated CD 45 as ‘Lean Republican’ (PVI: ‘R+3’) and CA 21 as ‘Likely Republican’ (PVI: ‘D+5’).

If Democrats flip the House in November, credit a diverse group of activists throughout the country, but count on middle-class women to drive the change. As Theda Skocpol describes the movement to resist Trump, “This will not look like a far-left reinvention of Tea Partiers or a continuation of Bernie 2016. It will look like retired librarians rolling their eyes at the present state of affairs, and then taking charge.”

Photograph: editor’s photo of January 20, 2018 Women’s March in Los Angeles.