Biden continues a run of strong state polls, as Democrats get good news in the Senate.

Another good day for Biden in Wisconsin: An ABC News/Washington Post poll Wednesday found Joseph R. Biden Jr. up by six points among likely voters in Wisconsin, putting him in a strong position in the state, hovering at or above 50 percent with a consistent lead in an unusual number of recent high-quality surveys. Wisconsin was a “tipping point” state in 2016 and many thought it would be a real challenge for Mr. Biden. The state’s white working-class voters swung hard to President Trump in 2016, and Mr. Biden seemed to be weaker in Milwaukee’s suburbs than in suburbs elsewhere. And the unrest in Kenosha seemed to give Mr. Trump another opening. But it didn’t lead to a change in the state of the race, and that might say something about the national political environment.

An eye-popper in Minnesota: ABC News/Washington Post also released a poll of neighboring Minnesota, showing Mr. Biden ahead by 16 points in a state Hillary Clinton won by under 2 percent. The poll is probably an outlier, but Mr. Biden’s lead in Minnesota is large, and it’s real.

An even bigger eye-popper in Maine: Quinnipiac released a poll of Maine with very strong results for Democrats: a 12-point lead for Sara Gideon, who is trying to unseat the incumbent Republican senator, Susan Collins; and a 21-point lead for Mr. Biden. A word of caution: Quinnipiac has leaned quite a bit to the left in this cycle.

A split between state and national polls? State polls this week have shown strong results for Mr. Biden. But national polls show stability, or even a bit of tightening. It’s hard to know what to make of the split. It could be just noise: The national polling is sparse and often of questionable quality. But there may be a real split, driven by demographics: Most of the great results for Mr. Biden in recent state polls have come in overwhelmingly white states, and there are plenty of national (and state) poll results suggesting that Mr. Biden is running ahead of Mrs. Clinton among white voters but faring worse among nonwhite voters. That could lead to seemingly surprising results for Mr. Biden in overwhelmingly white states like Minnesota and Maine without corresponding national leads. That would not necessarily be a bad trade for Mr. Biden. Mrs. Clinton probably would have traded a few points nationwide for greater support in the Midwest.