Nate Cohn article for NYTimes from Sept. 11, 2019

Moderate Democrats Fared Best in 2018

A North Carolina election is also a chance to think about what kind of candidate might do best against President Trump.

Dan McCready is the kind of candidate who helped Democrats win the House in 2018.

He’s a Marine Corps veteran who vowed not to support Nancy Pelosi for House Speaker. He doesn’t support “Medicare for all” or an assault weapons ban. And he came less than half a percentage point short of winning a fraud-marred election in a North Carolina district that voted for Donald J. Trump by 12 points in 2016. He’ll have another chance in the redo election of the state’s Ninth District on Tuesday.

As Democrats mull what kind of candidate has the best chance against President Trump, it may be worth considering which candidates fared best in last year’s midterm elections. Over all, moderate Democrats who disavowed Ms. Pelosi and Medicare for all fared better than those to the left of them, according to an Upshot analysis of the 2018 midterm results.

On the debate stage Thursday in Houston, many Democrats will be taking the opposite approach. Some of the debates so far have highlighted unpopular positions like busing, decriminalizing unauthorized border crossings, providing health insurance to undocumented immigrants and abolishing private health insurance.

If the Democratic nominee did wind up embracing a more left-leaning agenda, there is no way to be sure that there would be an electoral penalty. But decades of research suggest that ideologically moderate candidates tend to do well in American elections. The advantage of nominating an ideologically moderate versus an extreme candidate may be smaller in today’s more polarized era, but it still seems to exist.

In Republican-held congressional districts, the Democratic candidates who supported Medicare for all, for instance, fared as much as a net three points worse than those who did not, after controlling for other factors like recent presidential and congressional election results.

Candidates who supported Medicare for all probably differ in other ways from those who opposed it. But Medicare for all is a good proxy for a certain kind of candidate favored by the activist left, and that kind of candidate did a bit worse in last year’s elections.

Similarly, candidates who opposed Ms. Pelosi fared an additional 2.5 points better than those who did not, even after controlling for whether a candidate supported Medicare for all.

It is worth cautioning that the precise effects of moderation — here a cumulative five points compared with someone who supported Ms. Pelosi and Medicare for all — depend on several factors. It makes a difference whether you look at all congressional districts or just the relatively competitive ones (say, those Mr. Trump won by less than 20 points) where voters might have gotten to know the candidates. It also matters whether to include fund-raising success, because moderates tended to raise more money. But the advantage of moderation holds no matter the series of choices.

A substantial body of research shows effects fairly similar to what’s observed here. It’s also roughly equivalent to the gap between the front-runner Joe Biden and Bernie Sanders or Elizabeth Warren in national polls [....]

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