the Attorney General has received written meritorious complaints from residents, elected officials, or civic participation organizations that efforts to deny or abridge the right to vote under the color of law on account of race or color, or in contravention of the guarantees set forth in section 10303(f)(2) of this title are likely to occur; or

in the Attorney General’s judgment (considering, among other factors, whether the ratio of nonwhite persons to white persons registered to vote within such subdivision appears to the Attorney General to be reasonably attributable to violations of the 14th or 15th amendment or whether substantial evidence exists that bona fide efforts are being made within such subdivision to comply with the 14th or 15th amendment), the assignment of observers is otherwise necessary to enforce the guarantees of the 14th or 15th amendment;