There are two very different types of measures of this, one being polling that was done both immediately before and immediately after the debates, and the other being Google searches of the names both immediately before and immediately after the debates. This report will cover both measures, as of June 30th.
Regarding the polling-data, there is, as of this moment, only one poll that was taken both immediately before and immediately after the debates, and it was issued at 11:18 AM on June 28th, the morning after the second of the two debates. It’s from 538 dot com and Morning Consult. It was a very scientifically sampled poll throughout, and therefore is virtually definitive on the question regarding who actually won and lost from the debates. Presumably the big winner from the debates, who is unquestionably Kamal Harris, will now be collecting enormous infusions of money, and not only from the voters who will donate small amounts to her campaign, but especially from the billionaires whom she has especially been seeking to flood her campaign with money.
This — the most reliable of all measures of the winners and losers — can be found at the two web-pages:
UPDATED JUN. 28, 2019, AT 11:18 AM
Here its bottom lines are summarized, in numbers:
Biden before debates 41.5%, after 1st debate 35.4%, after second debate 31.5%
Sanders before debates 14.4%, after 1st debate 16.4%, after second debate 17.3%
Warren before debates 12.6%, after 1st debate 18.0%, after second debate 14.4%
Harris before debates 7.9%, after 1st debate 6.3%, after second debate 16.6%
Buttigieg before debates 6.7%, after 1st debate 4.4%, after second debate 4.8%
Biden’s new supporters come mainly at the expense of the few undecideds.
Sanders’s new supporters come mainly at the expense of Warren.
Warren’s new supporters come mainly at the expense of Biden.
Harris’s new supporters come mainly at the expense of Sanders, and secondarily of Biden.
Biden lost 10.0% from his pre-existing 41.5%, or -24% from his prior support.
Sanders gained 2.9% onto his pre-existing 14.4%, or +20% onto his prior support.
Warren gained 1.8% onto her pre-existing 12.6%, or +14% onto her prior support.
Harris gained 8.7% onto her pre-existing 7.9%, or +110% onto her prior support.
Buttigieg lost 1.9% from his pre-existing 6.7%, or -28% from his prior support.
Those are the main results, because those are the main four candidates, as of the present time, and because these numbers are the best indicators of the debate-performance. Harris’s more than doubling her support is an overwhelming indication that she will probably, as of the present moment, become the Democratic nominee, unless Sanders goes after her record ferociously and at least tries to end the big-money dominance of the Democratic Party (which she and almost all of the other candidates are courting). If he does that, then Sanders, who himself rejects the support from the big-money donors, including from PACs, will need to greatly boost his collections from the Democratic Party electorate and thereby cause that Party to go ferociously against the billionaires who have been controlling that Party (other billionaires control the Republican Party) and for a reformed Democratic Party that represents instead the public. This would crush Trump in the general election if it succeeds in taking control over the Democratic Party, away from its billionaires, which itself is highly unlikely to be able to be done. Consequently, as of now, the likeliest winner of the Democratic nomination is Kamala Harris, who would then become a second Barack Obama, not merely in the sense that he is a light-skinned Black, but that she is an enormously gifted politician who is in the pockets of that Party’s billionaires. Pete Buttigieg had been trying to be that, but his style isn’t even nearly as effective as hers is.
Another, and very different, quantitative measure of debate-performance is google-searches, which is the best single indicator of the Democratic Party electorate’s, and of of independents’, and even of dissatisfied Republicans’, interest in learning more about the given candidate. This is NOT at all similar to those polled numbers that were just summarized, because it indicates the responses of the entire American interested electorate, all of the potential general-election voters, the people who will be making the final choice on Election Day (assuming that the vote-counts on that day will be honestly tabulated). Therefore, this measure is NOT an indicator of the sentiments of pre-existing Democratic Party voters — the people who are generally polled such as in the numbers just indicated here. These numbers can be wildly different from those numbers, because:
“Among the public overall, 38% describe themselves as independents, while 31% are Democrats and 26% call themselves Republicans, according to Pew Research Center surveys conducted in 2018.” (An additional 5% are either “Other party” or “Don’t Know.”)
Consequently: If one of the Democratic Party candidates is drawing support mainly from outside the Party, then that candidate is drawing mainly from the 38% of independents and from the 26% of Republicans (i.e., from Republicans who disapprove of Trump) and from the 5% who are “Other Party” or “Don’t know.”). That would be drawing support mainly from the 69% of Americans who are NOT Democrats, instead of from the 31% who ARE Democrats. Consequently, the most-googled candidate might possibly represent the strongest general-election candidate, but is not nearly as likely to be the Democratic Party’s nominee, unless and until the candidate rises in the Democratic Party primary polls to become the most-supported candidate among Democratic Party primary voters.
Here are those figures, directly from Google itself, which is the only original source of the numbers:
First night June 27-30
• #1 Tulsi Gabbard
• #2 Elizabeth Warren
• #3 Beto O’Rourke
• #4 Cory Booker
• #5 Julian Castro
Second night June 27-30
• #1 Kamala Harris
• #2 Joe Biden
• #3 Marianne Williamson
• #4 Bernie Sanders
• #5 Pete Buttigieg
What is particularly striking there is that in these results, one candiate, Harris, is also the likeliest to win the Party’s nomination, but the other, Tulsi Gabbard, scores dismally low in the polled figures:
What all this suggests is that, whereas possibly the strongest general-election candidate against Trump would be Tulsi Gabbard, Kamala Harris, who is one of the billionaires’ candidates, also might be. A voter in the Democratic Party primaries who is mainly concerned about beating Trump should be supporting either of those two candidates to become that Party’s nominee. As regards what criteria that person would be applying, no intelligent voter any longer trusts a candidate’s mere words, but instead votes on the basis of that person’s existing record of actual actions as a public official. And, of course, a part of that record is the politician’s current policy regarding acceptance of PAC money, and the politician’s record of largest donors, especially in the latest campaign.
Here are Kamala Harris’s top donors.
34.87% come from donations smaller than $200. 57.78% come from donations larger than $200.
Here are Tulsi Gabbard’s top donors.
38.8% come from donations smaller than $200. 59.31% come from donations larger than $200.
Here are Bernie Sanders’s top donors.
75.55% come from donations smaller than $200. 22.81% come from donations larger than $200.
Here are Joe Biden’s top donors.
0.95% come from donations smaller than $200. 95.28% come from donations larger than $200.
Here are Elizabeth Warren’s top donors.
55.88% come from donations smaller than $200. 31.08% come from donations larger than $200.
Here are Pete Buttigieg’s top donors.
“Alphabet” is Google. Amazon is Amazon. Almost the entire list represent billionaires.
Investigative historian Eric Zuesse is the author, most recently, of They’re Not Even Close: The Democratic vs. Republican Economic Records, 1910-2010, and of CHRIST’S VENTRILOQUISTS: The Event that Created Christianity.