Republican Party leaders worry privately that the party is adrift since Chairman Lee At water has been sidelined with a brain tumor and they are concerned about the GOP's chances in November. Few Republicans are happy with New York gubernatorial candidate Pierre Rinfret. "At water would have made sure we had somebody decent "to challenge Mario Cuomo, says one GOP operative. And Atwater is where GOP leaders say "he'd be stoking the fires" for Gov. Bob Martinez. Private polls show "good news" for House Republicans who defy President Bush's flip-flop on taxes. But having to run against a Republican president is cold comfort for GOP strategists.