Nate Cohen, expert on polling and demographics:

The results suggest that Ms. Warren, who has emerged as a front-runner for the Democratic nomination, might face a number of obstacles in her pursuit of the presidency. The poll supports concerns among some Democrats that her ideology and gender — including the fraught question of “likability” — could hobble her candidacy among a crucial sliver of the electorate. And not only does she underperform her rivals, but the poll also suggests that the race could be close enough for the difference to be decisive. link

Warren will drop significantly more if nominated, from GOP attacks as a "tax raising big government elite east coast professor from Harvard", a "socialist", a "Maduro clone", "will turn America into Venezuela" etc. She has given the Republicans plenty of material to use against her in her 54 plans.  (yes, there are 54 of them) Even some of her single plans, like her 15,000+ word Medicare for All healthcare/tax plan make FDR's New Deal look like a business as usual continuing resolution. The Warren plan would kick 140 million or so off their current health care plans. Although some might not mind, millions who like their plans will mind. Many on Medicare may be concerned the system will go broke faster, leaving them at the end of the line.  Warren has no provision in the plan for anyone in the United States to pay anything per visit, which is an invitation to broken appointments and increased use of emergency rooms. There is no guarantee that doctors will not just opt out of the system and go full fee for service, causing further congestion at doctors still taking Medicare for All. It will overturn 18% of our economy and is sure to be a ripe target for all kinds of attacks from the Republicans and their PAC's.