Of course, but if he was to start a big argument with the Dems and give them a chance to start demagouging he might lose the votes of some middle of the road voters who change their minds more often than actresses' hair styles. He would also boost turnout amongst the Democratic base. He has no risk free decision.
I believe he feels he's taken a conservative stand on enough things, like his judicial appointments, tax cuts, missile defense, oil drilling in Alaska to name a few, to motivate conservatives to show up. For some conservatives nothing short of 100% is acceptable, but any Republican who wastes his time trying to convince them has rocks in his head. True Free Republic type conservatives are not the majority of the electorate. Bush has to live in the real world.