Never-Trumper and Trump-skeptical voters defied conventional wisdom last week: They mattered. Their numbers were small, but in tight races, suburbanite registered Republicans voted for Democrats over Republicans, helping to send them to Congress.

My colleague Ezra Klein wrote that the 2018 midterms marked the fall of the “not-quite Trumpers,” noting the loss of some of Trump’s biggest critics within the Republican Party and in Congress, like Sen. Jeff Flake (who retired) and Sen. Mark Sanford (who lost his primary). But Trump should remember that Never Trumpers and the Trump-skeptical — or as Henry Olsen called them in the Journal for American Greatness, “RINOS” (Republicans in name only) — still vote — and still matter.

As Olsen wrote, “The biggest reason Martha McSally lost is the same reason Republicans lost control of the House: RINOs. Across the nation, moderate college-educated independents who had frequently backed Republicans in prior elections switched sides.”

If he wants to win in 2020, Trump will need to win again in suburban areas in states like Pennsylvania, Wisconsin, and Michigan, and win with Trump-skeptical Republicans. The GOP’s problem in 2018 wasn’t just that Democrats came out motivated and in bigger numbers than in 2014. Their problem was that a small percentage of Republicans who don’t like Trump didn’t stay home — instead, they showed up, and they voted for Democrats.

The GOP may not want to acknowledge it. But if they want to win in 2020, they should.

“The reason for Republican success is undeniable: President Trump proved to be our closer and our game-changer, making a quantifiable difference in key races across the country.” -@kayleighmcenany — GOP (@GOP) November 12, 2018

Republicans helped flip a Senate seat to Democrats for the first time in 30 years

In races across the country, from Washington’s Eighth Congressional District (which had never sent a Democrat to the House before) to Virginia’s Seventh District, where the Tea Party captured one of its biggest wins in 2014, suburban districts with Republican tendencies went for Democrats in 2018 — with many conservatives clearly choosing Democrats over Republicans.

Democrats made historic gains in suburban districts of state legislatures - this set of maps shows just 57 of the gains. Of 57, ~23 voted Clinton/Romney & 10 voted Trump/Romney. Across 57, Clinton's '16 vote ranged from 43% to 60% #Election2018 #ElectionResults2018 #maps pic.twitter.com/JyU67SyZvw — Barry McMillion (@BMcM2018) November 9, 2018

Take Arizona, for example, where Democratic Senate candidate Kyrsten Sinema won 12 percent of Republican voters and 14 percent of those who consider themselves “conservative” — 1 percent more than what Hillary Clinton received in 2016 from the same group. And while those numbers may seem small, Sinema won her race by just over 35,000 votes. In a piece for Ricochet, conservative writer Jon Gabriel argued that Sinema’s victory over McSally, the Republican, was indeed due in part to frustrated conservatives, particularly moderates turned off by her later embrace of Trump (though ironically, McSally was accused of being a “Never Trump” Republican during the primary campaign.)

Sinema even won Maricopa County, the largest county in the United States to go for Trump in 2016; the second largest, Tarrant County in Texas, went for Democrat Senate candidate Beto O’Rourke over Republican Ted Cruz. Now, Sinema is the first Democrat headed to the Senate from the state of Arizona since Ronald Reagan was in the White House.

Or take Texas’s 32nd Congressional District, a suburban district outside of Dallas that FiveThirtyEight ranks as 9.8 percent more Republican than the country as a whole, a district in which the Republican incumbent, Rep. Pete Sessions, hadn’t faced a serious challenge to his House seat since 2004. But Sessions lost by nearly 20,000 votes to Democratic candidate Colin Allred, and while Sessions blamed his loss on “the liberal tide of people” who had moved to the region since 2010, the evidence doesn’t bear that out.

As NBC News’s Benjy Sarlin pointed out last week, the GOP’s losses in the suburbs in 2018 weren’t because the suburbs became flooded with Democrats, but because thousands of Republicans and independents who showed up to vote in record numbers both on Tuesday and in early voting voted for Democrats.

Hey you know what's an actual thing and not just a few people on Twitter? Never Trump Republicans. Everyone just internalized the idea these suburban voters are Democrats so quickly that they missed how Republican they were recently. — Benjy Sarlin (@BenjySarlin) November 9, 2018

But most importantly, Democrats swept upwards of 40 seats with extremely high turnout *from Republicans* at the same time. This wasn't just lifelong liberals showing up and conservatives forgetting to vote, it was defections from typical R voters. — Benjy Sarlin (@BenjySarlin) November 9, 2018

Conservative commentator Erick Erickson agreed, writing on Tuesday that Republican voters didn’t magically become liberals. “These voters in Texas, Arizona, Georgia, etc. didn’t become socialists in the last two years. They haven’t changed. They think the GOP has. Heck, the GOP lost suburbs in Oklahoma because of these issues. For God’s sake, people, a Democrat picked up SC-1 by running against Trump and tariffs and for free trade.”

And writing on the Republican’s massive losses in traditionally red Orange County, California, National Review’s David Bahnsen said on Thursday, “The fact is that a significant number of center-Right, fiscally conservative, suburban, upper-middle-class voters have found the present message of the Republican party repugnant.”

The research bears this out — and indicates that Democrats who promised to provide a check on Trump did better with suburban Republicans. According to the American Enterprise Institute, 38 percent of those polled (including Republicans, Democrats, and independents) said they voted to express opposition to Trump, with 26 percent voting in support of Trump and 33 percent saying Trump had no impact on their vote. (That 33 percent figure is the lowest since the 1990 midterms.)

The Never-Trump debate: vote for Republicans, or punish them?

But how Never-Trump Republicans and Trump-skeptical conservatives voted in 2018, and whether they voted for Democrats, isn’t just a matter of discussion for pollsters. A potentially shrinking base of votes for Trump is a real problem for the Republican Party — a fact GOP stalwarts like Sen. Lindsey Graham seem to have already recognized.

And more importantly, for many conservatives, the question of just how important Trump is to the GOP — and whether or not supporting Republicans is just supporting Trump by proxy — is one that threatens the very foundations of the Republican Party, which has existed for more than a century without Trump but now risks being defined solely by him. To be clear, the majority of Republican voters support Trump — but those who don’t, or once did but no longer feel the same way, still vote, and can turn the tide of both midterm elections and Trump’s eventual reelection campaign.

Before the midterms, some Never-Trump conservatives argued that the best way to stop the Trumpification of the GOP was to vote for Democrats. Among them was Tom Nichols, a professor at the Naval War College and the author of The Death of Expertise. He wrote a piece for the Washington Post titled, “Want to save the GOP, Republicans? Vote for every Democrat on this year’s ballot,” in which he argued that the Trump takeover of the GOP from the White House to Midwestern statehouses could only be stopped by rejecting the Republican Party, full stop:

Republican elected officials, from Congress to the state houses, have chosen to become little more than enablers for an out of control executive branch. The only way to put a stop to this is to vote against the GOP in every race, at every level in 2018. It’s tough medicine. But as someone who’s voted Republican for nearly 40 years, who favors limited government and public integrity, and who believes America still needs a credible, responsible center-right party, I see no alternative.

Nichols told me he believed that Trump — and moreover, how Trump’s base has shrunk — played a big part in causing some Republicans to vote for Democrats. “Trump’s capture of the GOP as a cult of personality — which I had thought not possible — goes right down to the local level, and so my guess is that many of these voters were not trying to send a message (as some of us Never-Trumpers were trying to do) but rather finding themselves defined out of the Trump base, which is increasingly white, male, and uneducated,” he said.

In Nichols’s view, “the most reliable way to moderate the GOP — at least in terms of its practical effect on national politics — is to remove it from the majority.”

Some other conservatives, like Robert Kelly, a professor of international relations in the department of political science and diplomacy at Pusan National University and a “lifelong Republican” who is deeply opposed to Trump, feel very much the same. Kelly told me that voting for Democrats was the only way to stop Trump. “One has to vote mechanically and straight-ticket for the Democrats — not just against the GOP, but for the Democrats, because only one large party in a bipartite system can check the other. This is the only way to send a national message to the GOP to pull over.”

For his part, Trump has shown no interest in reaching out to the Trump-skeptical, or to suburban voters, preferring to conclude that those who lost their seats in the 2018 midterms did because they didn’t embrace him enough — despite the fact that a number of races in which Trump intervened directly went toward Democrats.

But even other Trump-skeptical conservatives have argued against voting for Democrats to stop Trump, saying that either that Democrats presented an even worse option than Republicans or that the risk of losing “good Republicans” — their losses making the GOP even Trumpier — was too great for conservatives to vote for Democrats.

Earlier this month, National Review writer David French argued that Democrats had failed to do enough to win over Republicans, and wrote, “I refuse to recommend that anyone vote against a good conservative, including good conservatives who could remain in office long after Trump is gone from politics, to ‘punish’ the GOP.”

And Jonah Goldberg, another National Review writer who also has a weekly opinion column with the Los Angeles Times, wrote that voting for Trump-skeptical Republicans over Democrats would itself act as a bulwark against Trump: “If you think it’s bad for the country if the GOP were to become — in Max [Boot]’s telling — a ‘white nationalist’ party, shouldn’t you vote for the Republicans who would fight back against that?”

Goldberg told me he agreed that pushing back against Trump played a part in why some Republicans voted for Democrats. “If you just look at the kinds of Republicans who defected, there’s just not much on the policy side that would warrant it — with the important exception of the immigration stuff,” he said.

But he argued that many of those who voted for Democrats in 2018 may have been Trump voters in 2016. “Remember most, or at least many, of these suburban voters were almost certainly not Never-Trump voters in 2016. So they presumably voted for lower taxes and conservative judicial appointments,” and thus, voted for Trump. But since 2016, Goldberg told me, those same voters had gotten more than they bargained for from the president. “What they don’t like is the way Trump conducts himself as president and forces them to defend indefensible statements and behaviors.”

And unlike Nichols, who has left the GOP and believes that the party is “dead” (adding, “Even when Trump is gone, the populist dumpster fire he’s been fueling will smolder on”), Goldberg argued that by leaving the GOP to the Trumpists, that would in effect be dooming the Republican Party, and the conservative movement.

“I think the dilemma for a lot of Trump-skeptical conservatives is that if you completely abandon the GOP or even the conservative label, it becomes a self-fulfilling prophecy,” he said. “As my colleague Dan McLaughlin puts it, ‘I’ll be damned if they can have my party.’”

Goldberg added that he didn’t see space for himself and other conservatives among Democrats and liberals. “Democrats and most partisan liberals have shown zero interest in moderating their views to accommodate defectors. Instead, the defectors are expected to recant all of their views. I can’t and won’t do that. After all, the whole reason I haven’t jumped on board the Trump train is that I refuse to lie for him. I see no reason I should start lying to oppose him either.”