Senate Republicans narrowly defeated (by a vote of 50-49) a Democratic amendment that would have required states to continue contributing to welfare, child care and training programs in order to qualify for federal block grants. States currently provide 45 percent of welfare costs. Three GOP Senators -- Bill Cohen and Olympia Snowe of Maine, Jeffords of Vermont -- voted with the 46 Democrats. Continued Republican defections could frustrate Bob Dole's determination to complete the legislation by Thursday. Face with nearly 200 more amendments, he may punt, folding welfare reform into a mammoth budget reconciliation bill scheduled for a vote next month.