What to Watch For as Harris and Pence Visit Wisconsin on Labor Day

Labor Day is the traditional kickoff to the fall campaign season, but this year the holiday represents something more: the first time both candidates for vice president will be on the trail on the same day in the same state.

Vice President Mike Pence and Senator Kamala Harris on Monday will be on opposite ends of Wisconsin, a battleground that’s increasingly essential to President Trump’s electoral map.

There were a few more competitive states in 2016, but no loss was as devastating to Democrats as Wisconsin. Michigan they saw coming and raced in vain to salvage at the end of the race, sending former President Barack Obama and Hillary Clinton herself for 11th-hour rallies. And Democrats never took Pennsylvania for granted, with Mrs. Clinton and Mr. Obama concluding the campaign in Philadelphia on the eve of the election.

But Mrs. Clinton, confident in success after Mr. Obama carried the state twice with ease, (in)famously did not campaign in Wisconsin in the final stretch of the campaign. Mr. Trump captured just 47 percent of the vote, but that was enough to win the state by less than 23,000 votes. The race in Wisconsin, it turned out, was truer to what happened in 2000 and 2004, when the results were similarly close, than to Mr. Obama’s anomalous margins.