"Short on votes and beset by internal divisions, Senate Republicans struggled Tuesday to salvage a respectable defeat for a constitutional amendment banning gay marriage, an issue that President Bush pushed toward the top of the election-year agenda. "This issue is not going away," Majority Leader Bill Frist of Tennessee said in a virtual concession that the measure would fall short of the 60 votes needed to advance past a Wednesday test vote. "Will it be back? Absolutely, yes," he added.