The problem is that there is nothing within that spam message that identifies which alliances the senator is aligned to, and as such its possible that the voters may be voting for your senator when they would rather vote for one that their own alliance has approved. The fact that this information is missing is why people can misconstrue this as an impersonation of a purple unity member asking for the vote.
Other than that I dont see a real problem here, and nations should have the common sense to check whose alliance thatthe author of the message belongs to anyway, particularly if they are unfamilar with the sender.