How Joe Biden is eating into Bernie Sanders' coalition

(CNN)Since officially jumping into the 2020 race less than two weeks ago, former Vice President Joe Biden has reshaped the Democratic primary. His polling numbers have risen from the high 20s to the low 40s since declaring his candidacy two weeks ago. In doing so, Biden has, for the moment, left the rest of the Democratic field in the dust.

Perhaps surprisingly to some, much of Biden's newfound supporters seem to have formerly backed fellow 2020 contender Vermont Sen. Bernie Sanders, even though Biden backers are more likely to be more moderate, nonwhite and older than Sanders.' Obviously, some of this trend towards Biden and away from Sanders is because Biden is now receiving much of the news attention Sanders had been getting.
But something else is at play: Biden does well among whites without a college degree who, as a group, backed Sanders in 2016. This could help Biden given that other Democrats haven't been able to break through among white Democrats without a college degree in the primary.
Whites without a college degree still make up a substantial portion of the Democratic Party. Despite much noise about how whites with a degree are the future for Democrats, each group is about 30% of the party. Nonwhites, both with and without college degrees, are about 40% in total.
    To win in the primary, a candidate likely has to do well with at least two of these groups. So far, Biden's the only one to be doing that; he consistently has the support of African-Americans.
    Our latest CNN national poll shows Biden is strong with non-college educated whites, as well. Biden jumps from the low 20s among whites with a college degree to the mid 30s among whites without a college degree. Comparably, his lead over Sanders increases from only 5 points over Sanders among whites with a college degree to about 20 points among whites without a college degree. Sanders polls in the mid 10s with each group, though the sample size of these subsamples is small, which means we need to be cautious about extrapolating too much.
    When we look back at the average poll taken before Biden got in, we see both Biden and Sanders tending to do better among non-college grads. A Monmouth University poll conducted in late January, before either jumped in the race, for example, found that Biden scored 36% among non-college-educated whites compared to 22% among college-educated whites. Sanders went from 19% among non-college-educated whites to 12% among those with a degree.
    The effect of education among whites is also evident in early states, too. An April Monmouth poll from Iowa (where more than 90% of Democratic caucus voters will likely be white) showed that Biden climbed from 20% among Democrats with a college degree to 34% among those without. Sanders went from 13% to 19%.
    Biden's ability to breakthrough with non-college whites marks perhaps the biggest difference between the 2016 and 2020 primaries. In 2016, Clinton actually lost white voters without a college degree in the primary. Sanders beat her by 7 points among this group in the median Democratic nomination contest with an entrance or exit poll, even though she won college educated whites by 7 points in these same contests. Overall, Clinton defeated Sanders by 12 points in these states.
    The fact that Clinton couldn't win whites without a college degree was surprising at the time. After all, whites without a college degree tend to be more moderate and older -- two groups Clinton did very well among. Therefore, Sanders' strength among whites without a degree suggested real resistance to Clinton's candidacy from this demographic, resistance that carried through to the general election.
    Biden's connection with whites without a college degree is potentially very troublesome for Sanders. These voters are, after all, a better fit agewise and ideologically for Biden than Sanders. It's not difficult to see why some of them would be inclined to therefore go with Biden over Sanders, even if Sanders did well with them in 2016.
    Whether or not Biden's seeming appeal to white voters without a degree carries over to the general election is very much up for debate. He certainly would like to argue that, however, given how these voters moved toward Donald Trump in 2016.
      That appeal among whites without a college degree does help him for now in a primary in which most Democrats have been unable to break through with this group.
      Most of Biden's competitors -- like South Bend, Indiana, Mayor Pete Buttigieg and Sens. Kamala Harris of California and Elizabeth Warren of Massachusetts -- have only shown an ability to attract support among whites with a college degree. That's not going to be enough to win. If Biden's fellow Democrats cannot break through with non-college educated whites or nonwhite voters, Biden will hold onto the lead he has had since this race began.