Actually, the polling data (pathetic though it is) doesn't support your premise, i.e., that 'conservative' Republicans have become displeased with the President.
According to Pew, conservative Repubicans have remained staunchly supportive of the President (JA in high 80s); it's the liberal/moderate Republicans that have become less supportive (JA has 'slipped' to mid-70s).
NOTE: Pew contends that liberal/moderate Republicans comprise approximately 35% of the Republican base, while conservative Republicans comprise 65%.
But we do want him to be more assertive. Knocking Orca ,the Lying Whale, flat on his ass would be a good start.
Course..that's assuming one believes Pew. I'm not saying that liberal Republicans are not disenchanted, however, according to the mass media (ahem) conservatives have been so upset with Bush on domestic and SC nominee Harriet Miers. My guess is that with the liberal Republicans mad about Iraq and energy and the conservatives upset with domestic issues, Bush's numbers HAD to go down with Republicans, hence the larger population.
I still think that when he is out and engaged with the public, he "pulls" them back. When he is absent and appears "rudderless" he loses them...he needs to stick on the message that got him elected and keep reminding people about the facts. Counter the libs with facts!