In 2008 I think the Democratic Presidential nominee will get between 45%-48% of the vote in Arizona and should top 40% in Montana. There a number of states which will remain out of reach of the Democrats, however, a good Democratic campaign could hope to get over 40% of the vote in the following states (in order of likelihood) -
1. Indiana
2. Kentucky
3. Montana
4. Kansas
5. South Dakota
6. Texas
7. Alabama?
Alabama has probably topped out at 63% GOP given the large black population. Given the current candidates, I doubt they could break 40%, but the Republican could fall short of 60%.