Amnesty, specifically the GOP's and W's support of it, is what lost the GOP control of congress in 2006. That IMHO was really the nail in the coffin of the Bush administration.
These establishment Republicans never learn from history.
Our problem (myself included)is we think of Reagan as the rule rather than the exception. The Reagan presidency was fought tooth and nail by the establishment, many of whom are still in power today. Reagan had the same up hill battle that Ted Cruz will have getting the nomination, then getting his agenda through a GOP controlled congress.
The reason they don’t learn from history is echo chamber arrogance. They’re the elites.