By A. Shaw
DP Pollster Douglas Schoen writes:
“Telephone interviews with 400 likely caucusgoers in Iowa and 400 likely primary voters in New Hampshire, conducted Jan. 13-15, suggest that Ms. Warren is already considerably more competitive than national polls suggest. In a head-to-head Clinton-Warren matchup in Iowa, Mrs. Clinton ran 15 points ahead of Ms. Warren, at 51%-36%. Surprisingly, caucus-voting Iowa Democrats already appear to be thoroughly familiar with the Massachusetts senator, and well-disposed toward her, with a 75%-7% favorability rating. Mrs. Clinton has great favorables, too: 93%-6%.But Mrs. Clinton’s favorables don’t appear to make her invulnerable to a populist challenge from the left, as a Warren campaign would almost certainly be.”
A drop in  Clinton’s frontrunner status  makes all of the top contenders — Biden (15%), Warren (7%), and Sanders (5%) –  “more competitive.”
Warren says she isn’t a contender or even a future candidate. So, who — either Biden -or Sanders — gets her seven points? Sanders is a lot more similar to Warren than Biden. So, most likely, Warren’s seven points should be imputed to Sanders until the contenders announce their candidacy in March.
The results of Douglas Schoen’s “head-to-head” matchup between Clinton and Warren don’t demonstrate Warren caused Clinton’s developing crack-up.
Most likely, Clinton’s cracking-up mainly results from either Clinton herself with something like 38% in Iowa or Biden with 15% or Warren with 7% or Sanders with 5%. or a mix of these.