What we know about state of Dem primary

According to the Des Moines Register, nearly 75% of Iowans want at least some Democrats to leave the race. I feel their pain.

Some are plainly not serious contenders; others would do better to run for the Senate. It's difficult to follow the mob of candidates, but, realistically, only a fraction of the 23 candidates are worth tracking.

The Quinnipiac poll provides some guidance on the state of the race. We should caution that the results are not predictive but, by the same token, they shape coverage and fundraising.

For starters, former Vice President Joe Biden leads President Donald Trump 53% to 40% in a head-to-head matchup. Biden enjoys a huge lead among independents (58% for, 28% against). But he will not be able to rely solely on an electability argument so long as a whole bunch of other contenders would beat Trump comfortably. ("Vermont Sen. Bernie Sanders over President Trump 51-42 percent; California Sen. Kamala Harris ahead of Trump 49-41 percent; Massachusetts Sen. Elizabeth Warren tops Trump 49-42 percent; South Bend (Indiana) Mayor Pete Buttigieg edges Trump 47-42 percent; New Jersey Sen. Cory Booker by a nose over Trump 47-42 percent.")

The caution for Democrats not to discount the challenge they face is found in Trump's numbers on the economy. (Seventy percent of American voters say the economy is "excellent" or "good," though only 41% of voters say the president should get credit.) Moreover, with a margin of error of 3.5%, only four of the Democratic contenders safely best Trump.

In addition, Biden remains well ahead but is far from invincible. "Biden leads the presidential primary race with 30% among Democrats and voters leaning Democratic. This compares to his 35% standing May 21, his 38% standing in an April 30 Quinnipiac University National Poll, right after he announced his candidacy, and his 29% standing March 28." Sanders, I-Vt., has picked up a few points but is still at only 19%. Warren is closing fast at 15%, Buttigieg is at 8% and Harris is at 7%. You then have to drop to 3 percentage points to find former Rep. Beto O'Rourke, D-Texas. Everyone else registers at 1% or less.

This is a national poll, not a poll of early state voters. However, if the race stays where it is (unlikely), only six candidates would meet the 2% threshold for the September debates. Democratic voters should welcome that substantial reduction in the size of the field. Only then can most voters hear out the candidates at length in debates. It doesn't take a degree in political science to figure out that if one is at 0% or 1% and doesn't make a splash in the first Democratic debates at the end of June (hard to do when sharing the stage with nine other candidates), it probably marks the end of the road.

A few other pieces of data suggest places where the top candidates need to improve:

• Biden has a substantial gap between older voters (41% over the age of 50) and voters under 25 (31%) while Sanders has the reverse, drawing only 5% of those over 50 years old. Sanders does very well with respondents who say they are paying little or no attention to the race, while Biden does best with those paying a lot of attention. That doesn't bode well for Sanders.

• Buttigieg is not yet attracting nonwhite voters (3%) and his supporters tilt heavily toward "very liberal" while Warren's support is remarkably even across demographic lines and age groups, but her support among those making less than $50,000 (10%) is much less than that of wealthier voters. Harris trails Biden, Warren and Sanders among nonwhite voters. As a result, without much stronger support among blacks, Harris' path to the nomination narrows.

• In a matchup with Biden, Trump loses women - all women (34% for, 60% against) and white women (43% for, 51% against), whom he won with 52% in 2016. Trump can "spread the map" all he likes (so desperate they are to find states to replace those in which he is trailing badly) that the Trump team is reportedly spending money in . . . Oregon?!

• Warren, in a match up with Trump, does poorly with noncollege-educated voters (36% for, 56% against) and does slightly less well with women than does Biden (56% for, 35% against).

No candidate among the top six has a lock on any demographic group. Once the field narrows, you'll see perhaps significant shifts in their relative levels of support. Until then, the big polling takeaways are twofold: Biden is no lock, and only six at this point look like they've got a chance.

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