In 2016, Hillary Clinton infamously declined to make a campaign stop in Wisconsin. That decision proved disastrous, as Donald Trump stunned Clinton in the Badger State, along with Michigan and Pennsylvania, on his way to capturing the electoral college. Now, almost four years later, Democrats are at risk of overlearning from Clinton’s mistakes.

No primary ballots have been cast, but a consensus is already emerging that next year’s presidential election will be decided by fewer states than any election in recent memory: Wisconsin, Michigan, Pennsylvania and Florida. Democratic strategist Jim Messina, who managed President Barack Obama’s reelection campaign, said the circumstances dictate an unusually narrow playing field. “We are now looking at the smallest map in modern political history,” he told The Washington Post’s Dan Balz.

Based on this analysis, it is easy to envision Democrats investing a disproportionate amount of the party’s energy and resources into winning a few key battleground states in 2020. Indeed, Democratic hopefuls are already making frequent stops in the Rust Belt between visits to early primary states. Former vice president Joe Biden and Senator Amy Klobuchar (MN) have made their supposed appeal to Midwestern voters a central part of their “electability” pitch. “I’m accustomed to winning places like Pennsylvania and Ohio, Michigan and Wisconsin,” Biden boasted at a campaign stop this summer.

Read the full text of Katrina’s column here.