Clinton and Sanders are neck and neck as evidenced by the results from the Iowa Caucus. The divisive aspect of their personas is the idea that Clinton has become a Washington insider who is bent on keeping out people like Sanders. The scandal several months back involving the DNC and Clinton is evidence of this bias. A scandal of potentially purposeful voter fraud is another strike against Clinton as an honest representative of the people. It plays right into Sanders's hands.
The allegations of voter fraud in the Iowa caucus will not have any material affect on the Clinton campaign. The Clinton campaign has been the object of many negative allegations in the past and the general public forgets very quickly. The Clinton campaign also has a strong base of supporters that will not be swayed easily by voter fraud allegations.
I don't think these allegations of fraud in the Iowa caucus will influence the Clinton campaign in any way. Wait in some days and we will hear allegations of the same thing on the side of Bernie Sanders. It has always happened during elections and politicians will use the media to blast the others using that.
The Clinton campaign will be negatively impacted by this fraud. Voter fraud is a very serious, criminal accusation. Even though that the Clinton campaign will be negatively affected, Hillary should not be punished for it. What happened was Hilary's team had not done a full recount of voters and instead had added new people.