I think it varies by candidate.
For Fred Thompson it is to be himself. Continue to be a consistent, committed conservative.
For Mitt it is fooling enough conservatives into believing he actually is a conservative and will govern that way.
Here is the simple fact that make a man win the Presidency: LIKBABILITY, LIKABILITY, LIKABILITY.
He who connects better with the non political junkies who constitute 99% of the Republican base and the voting public in general and he who is liked most by them is going to win the Republican party nomination and the Presidency. People have to like someone first and connect to him and then they will analyze his message and his stands on the issues. The main reason why Hillary Clinton is not going to be elected President is that she is the most unlikable and meanest candidate to run for President.