Trump’s trying to dismantle the Blue Wall again. That would be disaster for Biden.

Joe Biden’s path to reelection has become increasingly clear: It’s the Rust Belt or bust.

The alternative route to the White House he appeared to break open in 2020 — winning Arizona and Georgia on the strength of changing Sun Belt demographics — would be far more challenging this time.

While polls broadly show Biden continuing to fall behind former President Donald Trump in swing states across the country, they consistently show the older, whiter states of Michigan, Pennsylvania and Wisconsin as the most competitive for Biden. Trump has larger leads in the Sun Belt states, in large part owing to Biden’s loss of support with younger voters and voters of color.

On Wednesday, Trump is spending his valuable day out of a courtroom visiting Michigan and Wisconsin. It’s another reminder that — even with the same two men as the major-party nominees — 2024 will be a very different election from 2020.

Trump won the three Rust Belt swing states in 2016, toppling what was once known as “The Blue Wall.” Wednesday’s visit comes as he’s trying to do so again — and Biden is forced to play defense, following the well-trodden path through the middle of the country instead of expanding the electoral map.

Trump holds leads over Biden of between 3 and 6 points in Arizona, Georgia, Nevada and North Carolina, according to FiveThirtyEight’s polling averages. The Rust Belt states appear more competitive: Trump leads by 1.2 points in Michigan, 1.8 points in Pennsylvania and 2.6 points in Wisconsin.

Biden can win without the four southern and western states — as long as he holds all three Blue Wall states and captures at least four electoral votes from Maine and Nebraska, the two states that currently award some of their electoral votes according to the winners of each congressional district. But if Trump flips any one of the Blue Wall states in that scenario, he’d be the next president.

Biden isn’t yet writing off the Sun Belt. His campaign continues to advertise in the same core, seven states it’s targeted for months: Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin. But there’s a clear divide between the Blue Wall states, where the polling is close, and the Sun Belt states, where it isn’t. And while each state has its own political dynamics, some of that divide is based on the composition of the electorate; Biden is being weighed down by his poor poll numbers with young voters and voters of color.

FiveThirtyEight’s database includes 19 polls so far this year in Arizona, 16 in Georgia, 12 in Nevada and 21 in North Carolina. Trump led Biden in every single one of those surveys. All four states rank in the bottom half of the nation by median age — and of the four, only North Carolina has a larger white population than the nation as a whole. (It also has a greater Black population share than the country overall.)

The three Blue Wall states are significantly older and whiter, and Biden hasn’t faded there as he has in the Sun Belt. He has occasionally led or tied Trump in polling this year in Michigan, Pennsylvania and Wisconsin — whether in head-to-head matchups or when Robert F. Kennedy Jr. and other third-party candidates are added.

Of course, relying on public polling to chart out each candidate’s clearest path to an Electoral College majority is not without risk. And the Blue Wall states, where Biden is closest, are also the same places where the polls were the least accurate in 2020, showing the Democrat in a more commanding position than the ultimate results. Biden won Pennsylvania and Wisconsin by just 1 point, and carried Michigan by 3 — despite leading by wider margins in preelection polling.

And abortion, which is roiling the state government in Phoenix, could help the president’s chances in Arizona, even as polls unanimously show Trump leading there.

Still, the signs of Sun Belt shifts and Biden’s durability in the Rust Belt are consistent with the national polling showing Trump making inroads with traditionally Democratic groups. The most recent New York Times/Siena College poll showed Biden with smaller leads than 2020 among voters under 45 (3 points), Black voters (60 points) and Hispanic voters (13 points) — important voting blocs in the southern and western battlegrounds.

Meanwhile, Biden is running stronger among demographics generally overrepresented in the Blue Wall states. Biden led by 9 points among seniors, a massive shift from 2020, and trailed Trump by 12 points among white voters, roughly identical to the 2020 result.

If Biden wins all of the three Blue Wall states, it would virtually assure his reelection, as long as either Nebraska maintains its proportional allocation method and again awards him one electoral vote or Maine counters Nebraska going to a winner-take-all method with a corresponding move. He wouldn’t need any of the competitive Sun Belt states — even Nevada, which Democrats have carried in every presidential election since 2008 but where Biden currently trails.

But if he loses all four competitive Sun Belt states, Biden can’t afford to drop any of the Blue Wall states. And given the size of Michigan (15 electoral votes) and Pennsylvania (19 electoral votes), it’s difficult for Biden to cobble together any Electoral College majority without them, even if he manages to hold Arizona or Nevada.