[Note: click on the graphs to get a full view including more-or-less readable data labels].
Here's a shout out to the graphic designers at the New York Times, who often produce great pieces of informational design, and who illustrated this op-ed about the black vote and the white vote in the Democratic primary. (I hope one of the data labels is in error: it cites the end of the graph as April 2, when the graph would really only be truly relevant if the end was May 2.) The article and the graphic make an important point: while the media has been fussing about whether Obama can win over white working-class men (many of whom will not vote for Clinton in the general election either), fewer observers of this political spectacle have been paying attention to the black votes that Clinton has been more or less deliberately throwing away and probably permanently losing.
The NYT article and graph are about a very specific question.
Contrast this to the more general and more common political discussion of whether a candidate is viewed favorably or unfavorably overall. Here's my quickly Excel-graphed illustration of Obama's approval ratings from November until now.
This graph uses overall national "approval" polling data from Rasmussen (the raw data are here) to show Barack Obama's approval ratings over time. The graph shows that the primary season has probably not had that much impact on how the overall electorate views Obama: mainly, people's views have on average become more certain (more "very" and less "somewhat"), but have not changed whether they like or dislike Obama.
The biggest shift came in late February where his "favorable" ratings got as high as 56% and his "unfavorable" ratings as low as 42%. In other words, the monumental flux of this campaign has been about 8% of voters who moved the center line between "kinda like" and "kinda don't like" back and forth.
My graph shows the effects of the political circus, the "who's up/who's down" tallies of cable news--and reveals a much more stable and enduring divide among voters, the one that persists election after election and actually does transcend personality. The smaller fluxes in "favorability" of any given candidate may or may not be important overall.
The NYT graph shows something more important: the actual effects of Hillary Clinton's behavior on a specific part of her base, and what could be one effect of her tactics if she were to win the primary. There is a significant inference here--the assumption that favorability ratings drive turnout. Maybe, maybe not. It may be that black voters would dislike her but vote for her anyway, which would probably be a rational choice. And there are a lot of things left unexamined in this graphic: it compares one group's view of one candidate with another group's view of another rather than comparing both groups' views of both candidates, which would likely be a more nuanced and less dramatic picture. Nonetheless, this single comparison and the clear presentation of the difference is much more interesting and reveals more significant shifts than where her favorability/unfavorability ratings have been going overall. (Not much changed.)
Sometimes smaller questions yield bigger answers.