Nate Cohn:

Mrs. Clinton is up by around seven percentage points in polling averages. But historically, a seven-point victory for the president’s party in the national popular vote is not the way to start a wave election. Richard Nixon’s huge victory in 1972 didn’t give Republicans the House. Neither Ronald Reagan nor George H.W. Bush took the House in 1984 or 1988. Bill Clinton didn’t retake the House in 1996.

The president’s party had down-ballot success in those elections, but gains were generally modest.

A Hillary Clinton landslide, though, might be likelier to result in a big shift in the House than in the past. That’s because the relationship between presidential and down-ballot vote choice has tightened. In 2012, President Obama’s share of the vote tracked very closely with the result of contested House races, albeit with Democratic and Republican incumbents tending to do a bit better. This is a long-term trend.

This is only a very small piece of the puzzle, but it’s an important one. There is less ticket-splitting than there used to be, so where a presidential candidate wins, members of their own party tend to win, too. More so than in the past, anyway.

That’s not necessarily great news for the Democrats though, since it remains true that their presidential candidates tend to roll up huge victories in cities and college towns while losing overall in the majority of congressional districts. The House gets competitive when the Democratic presidential candidate sweeps suburban districts, but the way the districts have been drawn makes it hard to get to a majority even in that scenario. It helps if they can cherry-pick a few deep red districts due to scandal, as they did in their 2006 takeover of the House. So far, that doesn’t look too likely this time around.

On the other hand, it’s a mistake to look strictly at the results of the presidential popular vote. What matters more than that is if there are a lot of people who decide to change their political affiliation. After Lyndon Johnson signed the Civil Rights Act of 1964, the behavior and allegiance of Southern Democrats changed dramatically. Barry Goldwater was crushed in the November election, but the states he won (other than his home state of Arizona) were all in the Deep South, previously the most universally and uncompetitive Democratic area of the country. Nixon was able to solidify that change and turn it into a landslide by 1972. Jimmy Carter temporarily reversed the trend by retaking the Deep South in 1976, but he lost it again and permanently for the Democrats in 1980. The flip of allegiance in the South came in fits and starts, and it wasn’t until after the 2002 midterms that the process was really complete on the Congressional level. This is why Nixon didn’t make progress in winning back the House in 1972 despite winning reelection in one of the biggest blowouts in American history.

Today, the Solid South acts as a bulwark for the Republicans instead of the Democrats, making it difficult for a Democratic president to move control of Congress even when winning in a Nixon-like landslide. There are other areas that seem impervious to national trends, too, mainly in exurbia, the Plains States, and parts of the Mountain West. Collectively, these areas make it appear impossible for a Democrat to win in nearly every state as Nixon did in 1972 and Reagan did in 1984. Perhaps a Democrat could max out at around 40 states, and in that case they almost definitely would carry Congress with them.

Donald Trump has shown some weaknesses in some of these areas. He’s unpopular enough with the Mormon community to make Utah at least an aspirational goal for Clinton, although she’d probably need help from third party candidates to give her a relatively small plurality win there. Erosion of the Mormon vote is probably more significant in states like Colorado, Nevada, and Arizona where Republicans can usually rely on their support to be close to unanimous. States like Wyoming and Idaho have too few Democrats to make a split in the Mormon vote much of a factor either on the presidential level or on the Senate or House level.

Trump is also showing weakness in the Deep South, particularly in Georgia, but also to some degree in South Carolina and Mississippi where the black vote is large enough to make even small cracks in the white vote a risk to Republicans. Another factor is the youth vote, which probably will be more Democratic in these Republican strongholds than it has been in the past.

Internal migration plays a role, too. Virginia, North Carolina, South Carolina, and Georgia have all grown more Democratic as many blacks have reverse-migrated to the South and the areas have attracted professionals from other areas of the country.

What really signals a blowout in the House races, though, is when a lot of people who were reliable voters for one party actually switch, and switch for good. The Reagan Democrats took a while to get around to doing that, but they played a huge role in the Republicans’ takeover of the House in 1994, and they have sustained their majorities ever since.

In this election, the wildcard of the youth vote is a factor. They’re wildcards because we don’t measure them by how they voted before, but by how they vote compared to the youth cohort they are replacing.

Suburbia is another factor, as Trump may get wiped out in suburbs from Cleveland to Atlanta, and those new allegiances may stick. It’s possible that much of suburbia will become much more likely-Blue than lean-Blue or toss-up in the future.

While I see it as less likely, the Mormon vote could remain a little more competitive, as least for a while.

One thing to keep in mind, though, is that we won’t see all the repercussions of the Trump candidacy in this year’s elections results, just like we didn’t see all the repercussions of LBJ signing the Civil Rights Act until nearly forty years had passed. We didn’t see shifting pro-Reagan allegiances manifest as Republican congressional majorities until more than five years after he had left office.

The youth vote of Reagan’s day supported him, and they remain largely loyal to the Republicans even today, but the same may be true of voters who came of age in the second half of the George W. Bush presidency or during the Obama Era. Thirty-five or forty years from now, these voters may still be loyal Democrats.

So, yes, even if Clinton wins this election in a blowout, she may not carry the House with her. But it still could be the beginning of a congressional realignment.

Having said that, most congressional landslides punish the president’s party. Most presidents see their party do very poorly in the first midterm election of the presidency. There are some exceptions, like George W. Bush’s post-9/11 successes in 2002, but that was probably a special circumstance. If Clinton wins the presidency, the chances are that the Democrats will lose seats in 2018, so this year is likely their best chance to win the House.

It still doesn’t look likely, but if it happens it will happen because a lot of people the Republicans thought they could rely on simply walk away from the party. And then the question will be, how many of them walk away for good?

Martin Longman

Martin Longman is the web editor for the Washington Monthly. See all his writing at