More people disapprove of President Clinton's performance since his Oval Office address last week entering the Administration in the tax-cut bidding war, according to a CNN/USA Today/Gallup poll released today. The poll of 1,016 adults, taken last weekend after Clinton's nationwide "Middle Class Bill of Rights" talk Thursday, showed Clinton's disapproval rating at 53 percent -- up from 50 percent in early December. His approval rating, meanwhile, remained at 42 percent over the same period. Clinton's lowest-ever mark, tabulated by the same pollsters, was a 54 percent disapproval rating last Sept. 6-7. Why? Most poll respondents (69 percent) said they believed the president was merely responding to Republican pressure for tax cuts. About 70 percent also said they favored spending cuts directed toward deficit reduction, rather than tax cuts. BTW: Clinton's highest approval rating came just a month into his presidency, when it reached 59 percent against a 29 percent disapproval mark.