By doing what he did best. Reagan bypassed the GOP and went DIRECTLY to the American People and talked to them in plain English about liberty vs. tyranny, keeping your money vs. sending it to distant bureaucrats, and giving America back to the American People.
Like Palin, Reagan had a bipartisan message of freedom from government coercion and regulations that resonated with the people.
Yeah, I know that, but he still had to get the nomination at the convention from people who were determined to nominate someone else.