Simply put:

1. There has been admitted voter fraud. One person even admitted to voting for Donald Trump in three different states.
2. Voters, including delegates, has been threatened by Donald Trump and his supporters.
3. The most-glaring example of voter fraud on the part of Reince Priebus and Donald Trump is that Washington, D.C.'s delegates 19 votes for Kasich & Rubio forcibly went to Donald Trump, even despite the protests of the 19 delegates from Washington, D.C..