WASHINGTON – The investment executive President Bush lauds while selling his Social Security overhaul suggested Thursday the White House drop its insistence on private investment accounts funded with payroll taxes if that prevents Democrats from supporting the effort. Bob Pozen, whose concept of “progressive indexing” for future benefits has become an administration favorite, said lawmakers should instead focus on so-called add-on accounts, which are funded with other revenues. The Boston investment chief has suggested increasing investment in Roth IRAs by lifting the existing caps on them. “Given the lack of bipartisan support for carve-out personal accounts, the president should not...