(CNN) Vermont Sen. Bernie Sanders , fresh off a devastating series of losses on Tuesday night, announced Wednesday afternoon that he was staying in the 2020 race (bet you didn't see that coming!) and looked forward to debating former Vice President Joe Biden on Sunday night in Arizona.

Sanders justified his decision to stay in the race -- despite trailing Biden by more than 100 delegates -- by noting that exit polling in the states that have voted so far has shown a) support for his liberal agenda (most notably his "Medicare for All" plan) and b) young voters preferring him to Biden.

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"What became even more apparent yesterday is that while we are currently losing the delegate count, we are strongly winning in two enormously important areas which will determine the future of our country," said Sanders in his hometown of Burlington, Vermont.

And he is right on both fronts.

Among voters aged 18 to 44, Sanders beat Biden 62% to 32% in Michigan -- even while losing the state overall by double digits. And again in Michigan, almost 6 in 10 (58%) said they preferred "a government plan for all instead of private insurance."

Those numbers -- on both the age and Medicare for All questions -- have been remarkably consistent across the states that have cast ballots in the Democratic primary to date.

But here's the problem for Sanders. Neither of them necessarily tells the full story of this election.

Let's start with the age question. Yes, it is true that Sanders has consistently beaten Biden among voters 18-44. But Biden has equally thrashed Sanders among voters 45 and older -- and that voting bloc has been much larger than the younger cohort.

In Michigan, for example, voters 45+ composed 62% of the electorate. In North Carolina, another swing state in the general election, 64% of the Democratic primary electorate was 45 or older. Ditto Virginia.

So sure, Sanders is winning younger voters. But younger voters aren't turning out in anywhere near the numbers that middle-aged (and older) voters are.

Then there is the Medicare for All question. What voters who take exit (or entrance) polls are asked is whether they support "a government plan for all instead of private insurance." Which doesn't get into the specifics of how people with private insurance would be required to give up their current insurance in order to become a part of the government system. Or that there would be no private health insurance at all.

That's not to say there isn't considerable support within the Democratic Party for Medicare for All. There is! But rather it's to note that simply pointing at this data point in an exit poll might not tell the whole story of how people feel about it.

Take a broader step backward. Even if you grant Sanders his two points about where he is winning, this fact remains: The Democratic nominee will be chosen solely by whoever gets the 1,991 delegates to the national convention. Winning certain demographic groups or certain policy fights is, broadly speaking, immaterial to who winds up as the nominee.

What Sanders was doing then was cherry-picking data that looked good for him. But it's not clear those data points show what he thinks they do or whether they matter at all in the hard delegate math that looks increasingly bad for him.