HOw the republicans can use electors to write in Pence.

http://electionlawblog.org/

Rick Hansen at Elelctionlaw blog has a couple articles about ways that the Republicans could use the Electoral College to try to get Pence instead of Trump as their candidate.

"But if Trump withdraws, and in fact even if he doesn’t, there is one other possible way out: the Electoral College. When we cast our votes for president they are actually cast for electors from each state (based roughly on population size) who then cast ballots for president. If Trump is chosen in some states, those electors could vote for Pence, or Romney, or Kasich, or whoever. There are some laws that bar “faithless” electors from casting votes for anyone who did not win the popular vote in a state, but I have a hard time believing either the Republican-controlled House or a court (because it raises a political question) would stop the actions of a faithless elector. Ned Foley games out how conflicts would work under the Twelfth Amendment; the bottom line is that if Trump got more votes than Clinton and Republicans control we could well end up with a President Pence. (When no one gets a majority in the Electoral College the House votes on a one state delegation, one vote rule.)"