The candidate behaviour literature, and the employment testing literature, is bulging at the seems with research on what is collectively referred to a "response distortion" in some instances, or "faking good".
The facts are that ANYONE who is applying for a position which they truly desire, will endeavour to present themselves as the person they believe the employer will want/like. We show up to the interview dressed more neatly than we probably would at a regular day on the job. We disguise the fact that we might be 3 months pregnant. We fail to disclose disabilities that are not immediately obvious. We adapt our style of speech to ingratiate ourselves with the host culture, and perhaps introduce some quips or humour that we feel will make us perceived as someone who will "fit in".
And whether it involves fitting in with respect to racial/ethnic aspects or something else (which candidate is NOT going to wear a modest western shirt and jeans at some point when campaigning in the western states?), all political candidates are going to try and be who their campaign organizers tell them the voters want them to be. The height of this silliness was, for me at any rate, illustrated by Mike Dukakis prancing around in military garb in a tank, trying to appeal to voters who view military strength as a desirable feature of a leader. It was like Joe Lieberman attending a hip-hop concert. While, as a non-American, I did not follow her campaign that closely, I am sure people will be able to point to examples of where Hillary Clinton was more feminine at one rally, to appeal to female voters, and more androgenous at others to appeal beyond female voters. During his campaigns, Bill Clinton was variously a legal policy wiz in high-end suit to appeal to the business community, and "aw shucks" regular guy at the burger joint to appeal to those voters. Then there was George Bush using Bruce Springsteen's "Born in the USA" at a rally to appeal to those voters. The list of "Zelig"-like transformations is endless and crosses party lines and historical eras. To pursue political office is to be a chameleon, and whatever shades or transmutations one has to adopt to acquire the magic numbers, one will adopt. That's just the facts.
So, is it likely the case that Barack Obama not only had/has solid leadership skills but also juuuuuuust the right degree of "blackness" (whatever the heck that is) to appeal to African-American voters, but not so much as to deter non-African-American voters? Yes. He's a good man, but I am confident there are other good men and women who were not nearly as electable. Reid's comments were about the role that race plays in electability, and in that respect, I find them neither racist nor uncalled for. There has not been a candidate for such a high office that straddled racial lines, so he has been an interesting case study. To notice that is not at all prejudicial.