They have the same right to express their political views and to support the candidates of their choice as anyone else does. I do think it ridiculous that a person would make a voting decision based solely upon the fact that a celebrity supported a candidate, party, or issue. If a celebrity is knowledgeable of the issues they should be respected as such. If they are not, this too should be taken into account.
Celebrities are people, just because they are famous doesn’t mean they don’t have the right to campaign for a political party. Sure they have to know what they are talking about because if they are doing it just because they are celebrities the shouldn’t’t campaign at all, we have to keep in mind that they have their own opinións but they have to use their opinions in their right way, they have more power than normal people. If they support something that is wrong or bad people might like it because a celebrety does it or supports it.
I think it's positive that celebrities are getting people to care about certain issues. I think that when they campaign for a political party it encourages more people to be interested in politics. Also, in America we have freedom of speech and if they want to express their opinions, they shouldn't be attacked any more than a regular person expressing their opinions (and we certainly have a lot of double standards for celebrities expressing their opinions) Some people argue that celebrities only support the Democrats because they pay them, but then again you could also say that rich people only support the Republicans because they pay them and poor people only vote democrat because it pays them.