Former vice president Joe Biden on Tuesday night continued on a trajectory toward the Democratic presidential nomination with wins in Michigan, Mississippi, Missouri and Idaho.

The wins mean Biden will extend his delegate lead over Sen. Bernie Sanders (I-Vt.) one week after initially gaining one on Super Tuesday, even as two states voting Tuesday have yet to be called: North Dakota and Washington.

Here are some takeaways.

1. The delegate gap widens

We don’t yet know the full results, but we can say with confidence that Biden’s delegate lead will grow substantially once we get them all. That’s because of both the trio of early wins in the "M" states — which made up 63 percent of the delegates available Tuesday — and the margins of victory.

Michigan and Missouri were very close between Sanders and Hillary Clinton in 2016, but the margins Tuesday were so big that Biden was called the winner in both shortly after polls closed. He wound up winning both by double-digit margins. There was also a chance that Sanders would fail to clear the 15 percent threshold for delegates statewide in Mississippi (he’s at 14.8 percent with 97 percent of precincts reporting). That would be yet another big setback for him, despite the state’s relatively small number of delegates (36). And Idaho was a particularly bitter pill to swallow, given he won its caucuses by 57 points in 2016 (the state now holds a primary).

When you throw all of that on top of the fact that the slow-counting California primary hasn’t produced the kind of delegate comeback Sanders was hoping for in the days after Super Tuesday, you start to see a yawning gap in the delegate race. All that remains to be seen now is how much the margin increased.

2. Michigan giveth, and Michigan taketh away

The Wolverine State was Sanders’s ticket to the party in 2016, with his shocking upset there — after polls showed him down by double digits — serving notice after Super Tuesday that Democratic voters weren’t quite ready to anoint Clinton. On Tuesday, it may have served the opposite function.

One of the more interesting findings in the exit polls was this: Among voters who decided on their candidate before this month, Sanders took a majority of voters, compared with Biden’s 4 in 10. But about half of voters said they decided this month — i.e., after Biden began his comeback with a big win in South Carolina — and they went for Biden more than 2 to 1.

In other words, Sanders was arguably primed to win the Michigan primary just 11 days ago, and then things changed a lot.

It’s an especially big win for Biden because he did it statewide and with surging turnout. While 1.2 million people voted in the state in the 2016 Democratic primary, that number was estimated at 1.7 million Tuesday. Part of that could have been that there was no competitive Republican contest and Michigan has open primaries. But in a state that Democrats badly need to win in the general election after losing it narrowly in 2016, expect Biden to make that part of his pitch: I can get voters to the polls in Michigan, because I just did it.

3. Sanders hits his demographic wall again

It was incumbent upon Sanders at the start of this race to build on his 2016 coalition — or hope for the crowded race to last longer. But now that the field is down to two candidates, two big, familiar problems remain for Sanders.

The first is his performance among black voters. His inability to win them over in 2016 was pretty much fatal in his race against Clinton. And now that it’s just him and Biden, the story is virtually the same if not worse. In Mississippi, he took 11 percent of the black vote in 2016 and was taking 10 percent Tuesday, according to exit polls. In Missouri, he took 32 percent in 2016 and was taking 24 percent on Tuesday. In Michigan, he stayed at 28 percent.

The other is his reliance on younger voters. Sanders’s campaign has argued that he can win in the general election because of his unusual appeal to this low-turnout group, but that hasn’t panned out in the earliest contests. And it deserted him again on Tuesday. Voters aged 18 to 44 were 40 percent of the vote in Mississippi in 2016, but just 32 percent on Tuesday. In Missouri, they were 41 percent in 2016 and 32 percent on Tuesday. In Michigan, youth turnout was the reason he pulled a shocking upset in 2016, but 18-to-44-year-olds’ share of the vote dropped from 45 percent then to 38 percent on Tuesday.

Given that, Sanders needed to expand his appeal to older people and to working-class white voters, but he’s regressed on both of those, too.

4. The calendar is turning in Biden’s direction

As ominous for Sanders as what happened Tuesday night was this: It might have been his best shot at actually getting back into the race this month.

In 2016, Sanders carried four of the six states that were up Tuesday — the three yet-to-be-determined states and Michigan. He also came within 0.25 percent in Missouri. The opportunity was there, but he lost ground.

Next week, by contrast, the primaries will be Arizona, Florida, Illinois and Ohio. Sanders lost all of them in 2016, including three of the four by double digits. All of them are demographically tough for him, for varying reasons, and all of them are relatively big delegate prizes, with about 200 more delegates at stake than there were on Tuesday night.

Then the week after that comes Georgia, a state with a large black population and many delegates.

So it becomes very difficult to see how Biden doesn’t come out of this month with a large delegate lead. Sanders needs to do something to change the race in a big way, but it’s not clear that he even has the opportunity over the next two weeks. His best chance is Sunday’s debate, but many votes in Tuesday’s races will already be in the books by then.

Also consider this: The only states Sanders has won east of the Mississippi River are his home state of Vermont and the neighboring state of New Hampshire, which was very close. There simply aren’t enough people in the western part of the country for Sanders, especially with California out of the way.

5. Biden’s electability case grows

It wasn’t just the surge in turnout in Michigan. Biden’s wins also spanned the Democratic electorate in one very significant way.

The following is true in at least the three states that Biden won early Tuesday night: He won nonwhites who went to college and those who didn’t — no surprise there — but he also won whites who went to college and those who didn’t. The closest he came to losing any of them was in Michigan, where non-college whites were somewhat close.

You can’t directly translate primary results to the general election, but for a Democratic Party that is twitchy about putting forward an electable candidate, you could do a lot worse than showing that kind of appeal to all corners of the party.