We now have two full weekends' worth of post-debate national polling out, so I think we can now safely assess what the impact has been.
Real Clear Politics pre-debate polling average:
So basically, there's now a somewhat closer race that includes a virtual three-way tie for second, with all the other candidates polling basically where they did before the debate: in the single digits. Most of the difference is obviously attributable to Harris's debate performance, which has enabled her to win over many of Joe Biden's supporters in particular. The debate doesn't seem to have had a major effect for Elizabeth Warren, but her previous trajectory of slow but steady polling gains, substantially at the expense of Bernie Sanders, has continued. (In other words, Warren's momentum appears to be less dependent on debates than Harris's.) I think it's worth noting those specific dynamics...
Biden voters --> Harris camp
Sanders voters --> Warren camp
...because they suggest one potential future for this campaign. Namely, in one potential eventuality, Kamala Harris and Elizabeth Warren could emerge as the two finalists competing for the Democratic nomination, with Harris as the default candidate of the neoliberals and Warren as the candidate of the progressives. That situation would mark a definite shift leftward for both ideological camps, and therefore also for the center of political gravity in the Democratic contest itself.
How would such an eventuality shake out? Who would most likely win in that situation? It's impossible to tell at this stage, though I suspect it would be Harris. The Democratic Party, since the early 1970s, has been composed of three main groups -- women, younger voters, and people of color -- with the victor of the Democratic primary battle usually being the candidate who wins over the balance of two of those groups. For example, in the 2016 Democatic nominating contest, Hillary Clinton won the balance of women and voters of color, while Bernie Sanders had the balance of youth support. In 2008 likewise, Barack Obama won over voters of color broadly and also younger voters, while Hillary Clinton won among female voters. (Incidentally, the candidate most favored by working class people lost in both cases.)
As things presently stand, between the Biden rivals, we see Kamala Harris leading among Democratic-leaning people of color, Elizabeth Warren among women, and Bernie Sanders among younger voters. Younger voters would be competitive, and potentially decisive, territory in a Harris vs. Warren primary battle. That's the main group who they'd both be competing for most likely, but female voters may also be moveable in either direction. Harris, however, would have the advantage overall in that Warren to date has a polling weakness among voters of color that Harris doesn't, so that group would probably be less moveable than the other two. Harris would also have the advantage of just being somewhat more palatable, I think, to the business world, and therefore would likely win the "electability" argument.Last edited by Jaicee - on 13 July 2019