President Bush may be making headway on the thorny issue of prescription-drug benefits for seniors by playing against type. Rather than foisting his demands on Congress as he did with the tax cut Bush has left it to the House and Senate to come up with a plan. Sure enough, the leading Republican and Democrat on the pivotal Senate Finance Committee last week forged a compromise that is drawing a surprising amount of support. The measure, which for the first time gives outpatient-drug benefits to 40 million Medicare recipients, isn't everything Bush wanted. While it offers incentives larger benefits to those who join private health plans those inducements are smaller than the White House would like. And the plan may cost too much; this week the Congressional Budget Office will determine whether its price tag pushes Medicare's cost over the $400 billion allowed by Congress for reforms. Still, the proposal is winning encouragement from the White House as well as from Democratic veterans of the health-care debate like Senator Ted Kennedy, who now seems less likely than the White House had feared to lead a filibuster against a Bush-backed plan. "It's a long process, but this is a big step," says a top Senate aide. President Bush will hit the road this week to start a campaign for Medicare reform but don't expect him to talk specifics. It's worked so far.