There are some back stories that explain the motivation of the Republican presidential candidates.
Mitt Is Still Proving Himself to Daddy
Paul the Anarchist
Ron Paul has said that the Civil War was wrong because the government had no right to end slavery, although he would not have been against people buying slaves to free them. He has opposed the Civil Rights Act because he believes people should have the right to indulge their race hatred without interference. These opinions has made Paul a hero to neo-Nazis who don't want anarchy so much as an oppressive dictatorship.
Book Tour Campaigns
Herman Cain and Newt Gingrich independently came up with the same brilliant plan to con people into donating money to pay for their book tours by pretending to run for President. Neither expected nor wanted to be declared front runner but it has helped book sales.
Bachmann and Santorum are just perpetual scolds who want a wider audience for their reproval.