First, analysts need to understand that the Republican base is furious with the Republican establishment, especially over the Bush years. From the point of view of conservatives I’ve spoken with, the early- to mid-2000s look like this: Voters gave Republicans control of Congress and the presidency for the longest stretch since the 1920s.
And what do Republicans have to show for it? Temporary tax cuts, No Child Left Behind, the Medicare prescription drug benefit, a new Cabinet department, increased federal spending, TARP, and repeated attempts at immigration reform. Basically, despite a historic opportunity to shrink government, almost everything that the GOP establishment achieved during that time moved the needle leftward on domestic policy. Probably the only unambiguous win for conservatives were the Roberts and Alito appointments to the Supreme Court; the former is viewed with suspicion today while the latter only came about after the base revolted against Harriet Miers.
The icing on the cake for conservatives is that these moves were justified through an argument that they were necessary to continue to win elections and take issues off the table for Democrats. Instead, Bush’s presidency was followed in 2008 by the most liberal Democratic presidency since Lyndon Johnson, accompanied by sizable Democratic House and Senate majorities.