People do not want to see a Presidential candidate looking sick and frail, so I believe this will affect the race. Sure, diehard Clinton supporters won't change, but it could affect some swing voters. The main thing that is the issue is secrecy. I don't know anyone in real life who thinks that Clinton really has pneumonia.
I believe that the winner of the presidential race is already pretty much determined by now. A bit of health scare on Clibton's part can do little to alter the pace of the presidential race. While it might effect doubts amongst voters, it seems like it was just a little illness and should have no effect.
Although it was revealed that Clinton has walking pneumonia, this health scare will not affect the presidential race. Clinton supporters know that this is a common ailment and not a serious medical condition. Trump supporters will see it as additional reasons to vote against Clinton, changing nothing in the outcome of the presidential race.
Hillary Clinton's health scare will not be a factor in this year's presidential race. People who don't like her and find her untrustworthy have already formed that opinion and will not vote for her. Others find her issues a product of the right wing media. In today's politics, it is polarized, with those likely to vote for their party's candidate no matter the circumstances.