When protesters swarmed major airport like Dallas-Fort Worth, New York-JFK and San Francisco International January 2017 to decry President Trump's ban on travel from predominantly Muslim countries, it presaged the contentiousness that has come to define his first term.
But it also highlighted an emerging electoral trend: the growing chasm between highly multi-cultural metro areas with direct links to other continents and the rest of the country.
America's political divide is often characterized as urban versus rural. But truly rural areas are a relatively small slice of the electorate: in 2016, only 14 percent of all voters cast ballots in counties defined by the Census Bureau as non-metropolitan.
Instead, the most significant divide in 2020 could be between the large, diverse metro areas that make up the majority of vote on America's coasts and the smaller, less diverse metro areas that are less likely to have reaped the benefits of a globalized economy. And Democrats' ability to defeat Trump in the Electoral College depends on whether they can hold their ground in the metro areas served by airports that don't have a lot of international flights -- but had a runway long enough to land Trump's Boeing 757 for a rally in 2016.
An analysis of flight schedules for U.S. primary commercial airports, Census data and election results yields a stark portrait of Democrats' challenge in 2020. For a moment, let's divide the country's electorate into four geographic tiers:
- Global Metros: Roughly 41 percent of the country's electorate resides in large metropolitan statistical areas (MSAs) served by airports with at least two regularly scheduled flights to destinations outside North America. Examples include Los Angeles, New York, Chicago, Dallas, Atlanta, Miami, Minneapolis and Seattle.
- International Metros: Another 14 percent of the country's electorate resides in metropolitan areas served by airports with at least one regularly scheduled international flight but fewer than two intercontinental flights. Examples include Indianapolis, New Orleans, Nashville, Kansas City, Pittsburgh, Columbus, Raleigh and San Antonio.
- Regional Metros: Another 31 percent of the country's electorate resides in metro areas served by airports featuring service from at least one of America's four largest domestic carriers - American, Delta, United or Southwest - but no international flights. Examples include Des Moines, Flint, Toledo, Buffalo, Pueblo, Erie, Little Rock and Spokane.
- Non-metro areas: Finally, 14 percent of the country's electorate resides in counties defined as non-metropolitan by the Census Bureau. Very few of these areas are directly served by major airlines, save for vacation destinations like ski resorts. These rural areas make up the majority of the population in states like the Dakotas, Vermont and West Virginia, but they comprise a much smaller share of the population in most larger states.
The good news for Democrats? President Trump is downright toxic in "Global Metros," the largest component of the electorate.
In 2016, Hillary Clinton took 62 percent of all major-party votes cast in these mega-cities and their suburbs, exceeding Barack Obama's shares in 2008 and 2012 as well as her husband's showings in 1992 and 1996. These are urban/suburban melting pots where Trump's rhetoric about immigrants and exhortations for non-white congresswomen to "go back" to other countries backfire. Of the 43 House districts Democrats wrested from GOP control in 2018, 28 were wholly or partially located in these metro areas.
Additionally, Democrats are holding their ground in "International Metros." In 2016, Hillary Clinton took 52 percent in these second-tier metropolises, roughly the same share Barack Obama took in 2012 and Bill Clinton took in 1992.
The bad news for Democrats? They are backsliding in "Regional Metros" - the smaller cities and suburbs where residents would have to connect through a larger hub airport to travel internationally, and where Trump's hard line on immigration and protectionism are likelier to resonate. In 2016, Trump took 55 percent of the vote in these metros, up from Mitt Romney's 53 percent in 2012 and John McCain's 51 percent in 2008. And, Trump clobbered Clinton in non-metro counties, taking 67 percent, up from Mitt Romney's 60 percent.
But the even bigger problem for Democrats: the "Global Metros" where Trump's unpopularity continues to deepen are disproportionately concentrated in states that aren't poised to be decisive in the Electoral College in 2020.
For example, residents of "Global Metros" make up 76 percent of the vote in California, 66 percent in Illinois, 97 percent in Maryland, 64 percent in Massachusetts, 89 percent in New Jersey and 61 percent in New York - all states Democrats win comfortably anyway. They're also 50 percent of the vote in Texas, a state where Democrats are on the rise but Trump still won by nine points in 2016.
But they're just 46 percent of all the vote in Florida, 48 percent of the vote in Michigan, 34 percent of the vote in North Carolina, 34 percent in Pennsylvania, and five percent in Wisconsin - all states that could be near the tipping point of the Electoral College in 2020.
Meanwhile, "Regional Metros" and non-metro areas - the places where Trump achieved liftoff in 2016 - are just 45 percent of the electorate nationally, but they're significantly over-represented in the most critical battlegrounds: they make up 52 percent of the vote in Michigan, 59 percent in North Carolina, 46 percent in Pennsylvania and 68 percent in Wisconsin.
Of the five states the Cook Political Report rates as 2020 Toss Ups, Arizona is the only state where residents of "Global Metros" make up a majority, 66 percent - a statistic inflated by the fact Phoenix's Maricopa County is home to a majority of the state's population.
Democrats have declined most sharply in rural America, but it's "Regional Metros" that should concern the party most in 2020. Not only do these smaller cities and suburbs make up an outsize share of the vote in key states - compared to both rural and "Global Metro" areas - but Democrats still have plenty of room to fall from Clinton's 45 percent share in 2016. If Democrats can maintain their altitude there, their gains since 2016 in "Global Metros" should be enough to overtake Trump and reoccupy Air Force One. If they can't, Trump could very well win reelection while losing the popular vote again.
For now, Democratic primary candidates are drawing enthusiastic crowds to rallies in places like New York, Seattle, Austin and San Francisco. But to beat Trump, Democrats will need to ask themselves which candidates' proposals will fly in Erie, Saginaw and Green Bay.
Note: all election statistics in this analysis refer to shares of the two-party vote.