With one day to go until five states are set to vote in tomorrow’s Super Tuesday contests, Bernie Sanders seems to be picking up support across several states that just a week ago were considered long shots for his campaign.

His biggest gains are in Illinois, where the Vermont senator was once down by as much as 37 points. Now he’s leading Clinton by 2 points (48 to 46 percent) in the latest CBS poll, out Friday.

In Ohio, Clinton still holds a lead. But that advantage has narrowed from about 30 points a week ago to about 6 points (49 to 43 percent) in the latest polls to come out, conducted by Quinnipiac, PPP, and CBS News/YouGov.

And in Missouri, where reliable polling has been scarce, Clinton appears to be leading by 7 points (47 to 40 percent) in a Fort Hays State University poll conducted of the race — but that’s within the poll’s huge 8-point margin of error.

Though Sanders seems to have pulled ahead from where he once stood, it’s still true that Clinton looks to be in the favorable position in most of these polls. Indeed, FiveThirtyEight’s election tracker lists each of these Midwestern races as likely wins for Clinton: She has a 98 percent chance of winning Ohio, a 95 percent chance in Illinois, and an 81 percent chance in Missouri.

But looking back just a week, FiveThirtyEight’s same forecasting model predicted a Clinton win in Michigan with greater than 99 percent certainty; most polls showed her ahead there by commanding double-digit leads.

Yet she lost in the state — likely due to an unexpectedly large turnout of young voters, white men, and independent voters. FiveThirtyEight called it "one of the greatest upsets in modern political history."

So the question remains: With polls tightening in the three Midwestern states whose demographics and economic landscapes more closely track Michigan, could Sanders pull off another upset — or possibly more than one?

Clinton, detecting danger, has already changed course in her campaign strategy, speaking more directly to people who are struggling economically. But polling is too scarce to measure the effect of the past few days of campaigning, and after polls failed to predict Sanders’s margin of victory in Michigan, it is wise to cast a wary eye on their predictions in similar states.

To be sure, if Sanders does win any or all of the Midwestern states voting on Tuesday, he will likely win by a similarly small margin, like the 2-point margin he won in Michigan. That’s not nearly enough for him to have a real shot at the nomination, since he is still very much behind in the overall delegate count (even not counting superdelegates).

If Sanders hopes to match the delegate lead Clinton has amassed, he’ll likely need to win most of the remaining states and take landslide victories in the heavily white states yet to vote.

That’s still technically possible. But with Clinton facing more certain victories in Florida and North Carolina, the other two states set to vote tomorrow, it’s looking like a tall order.

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