The appeal of RP is mainly to single issue voters. Today, more and more Americans have only one or two issues they vote on. If you are a person with a strong single issue such as pro-life, Second Amendment, anti big government, for lower taxes, small business, secure borders, anti war, anti war on drugs, etc, you will want RP as president.
Consequently, RP bring out voters neither of the big front runners will touch due to this single issue factor. So, many voters will come out that would otherwise stay home. If you always vote the party line, or want the lesser of two evils, you will likely stay with mainline candidates.
RP's chances hinge on press coverage. Currently the Associated Press has been very good with him. Other news outlets still have him on the wacko watch list.
Right now RP is a long shot. But, if he does a fourth place in either New Hampshire or Iowa he's a contender. Also, can he keep internet donations coming in? If he has money, he's in the ring.