I think it’s tactically brilliant. By nominating a qualified but recordless (where did he find this guy?) judge he puts the Democrats in a very difficult position.
Bush will probably have 3 opportunities to nominate judges. The Democrats have a limited amount of resources to expend fighting the nomination. If they adopt a scorched earth policy on Roberts they will have nothing left PR-wise should Bush nominate a more naturally appealing candidate (i.e. black/female, aka Janice Rodgers Brown) as his next nomination.
Most likely they will play this one very mellow and save all their capital for the next fight.