No, Trump is far more liberal than W if we take it on a conventional, issue-by-issue basis.
What matters far more to the GOP today is kicking @ss as opposed to specific policy positions. A high-energy Jeb Bush (lol) could easily have blasted Donald Trump despite having very different positions.
Keep in mind that W has a very high favorability rating among registered Republicans.
Which is where the GOP has gone through the looking glass. "What matters isn't what you say but how loud and angry you yell it" has to be about the world's most unconvincing argument ever.