Bush knows exactly what he's doing. He is trying to be all things to all people. He knows, or feels confident, that he has the conservative base in his pocket due to a recent poll. He also knows that he needs to pick up as many seats in the Senate and House as he can to have any hope of pushing through his conservative agenda before 2004. This is why he is leaning to the left on such issues as global warming and illegal immigration. He's hoping Hispanics and moderates will put the republicans over the top in the mid-term elections.
However, this 'strategy' will all far apart if his base abandons him over passing most of the democrat’s agenda.
In November we'll see if his strategy has worked.