Democrats are having a wonkish but important debate right now as they pick their next standard-bearer:

Should they try to persuade voters who supported President Barack Obama for two terms and then left them in 2016?

Or should they mobilize the tens of millions of Americans who stayed home in 2016 and would seem to have a natural home in the Democratic Party in 2020, including people of color and single women?

The debate tends to track along ideological lines. Progressives pushing socialized medical insurance are ready to forgo any attempt to win back Trump voters. Doing so allows them to claim that there's no electoral advantage to moderation. They think a robust progressive agenda will bring out Democrats who stayed home in 2016.

Moderates believe their policies can win back these Obama-Trump voters, who are usually whites without college degrees — many of them in the crucial "blue wall" states of Pennsylvania, Michigan and Wisconsin, but let's also throw in Minnesota.

Nationally, whites without college degrees are 45% of eligible voters, a declining but still massive plurality. This is President Donald Trump's strongest demographic. In the blue-wall states, their numbers are even greater — which is why Trump has an electoral college advantage even if he can't win a majority of voters nationwide.

In Minnesota, after the 2018 election, a DFL operative showed me results that averaged the statewide DFL result, after removing Sen. Amy Klobuchar and Attorney General Keith Ellison, the two outliers. The DFL won 10 counties that Trump carried in 2016. Then there were the counties where they had a 10 percentage point improvement or more over 2016: Red Lake, Kittson, Koochiching, Lincoln, Murray, Marshall, Jackson, Norman, Renville and Blue Earth.

Given that these counties usually have high turnout, there wasn't much room on the mobilization side. This indicates there must have been quite a bit of persuasion going on.

The mobilization argument hangs in part on the idea that there are no swing voters anymore. (See last week's column, which pretty much made that case.)

"We have an electorate as polarized as it's ever been," said Jennifer Duffy, senior editor of the Cook Political Report. The best evidence: every 2016 Senate race went in the direction of the presidential contest.

But even in small numbers, swing voters can flip an election. And their numbers, while smaller than in the past, are still substantial. Geoffrey Skelley of the University of Virginia Center for Politics used three separate data sources to conclude Trump scored somewhere between 6.7 million and 9.2 million Obama voters. They are concentrated in the crucial states that will decide the election.

Also, it just seems curious what you're doing as a political party if you're not trying to persuade people join you.

A future column will make the case for mobilization.

J. Patrick Coolican 651-925-5042 Twitter: @jpcoolican patrick.coolican@startribune.com