It's been pointed out to me (hat tip to dolphin_of_france) that some recent polling puts Warren ahead of Biden in the Democratic primary voting intention.
How sudden was this change? How much [of this] change happened in the time proximity of the recent Trump-Zelensky phone call disclosures?
Interestingly, as CNN noted about Warren (on Sep 23):
She has also been very outspoken on another issue supported by approximately 70% of Democrats: Impeaching Trump. Warren was the first major presidential candidate to call for impeaching the President back in April, just days after Robert Mueller's report was released. And on Friday after allegations were reported that Trump spoke to the Ukrainian President in July and pressured him to investigate Biden and Biden's son Hunter in an obvious effort to get dirt on Biden, Warren went a step further. She took to Twitter slamming Democrats in Congress for failing to act [...]
CNN then contrasts that with Biden's more cautious approach.
As it's been pointed out to me below, I should also be asking how reliable/relevant these polls are. Apparently they are state-level polls.