Until last weekend, President Bush had repeatedly fallen short in seven months of battles with a Democratic-led Congress that would not give him what he wanted on immigration or education, health care or energy policy.But the Congressional vote that authorized eavesdropping without warrants on international communications, including those involving Americans within the United States, has shown that there is at least one arena in which Mr. Bush can still hold the line: terrorism. (See, "Democrats, Republican accusations of being weak on ...")But while the Democrats had hoped to leave town for the August recess on an upbeat note, Mr. Bush and his party succeeded in outflanking them with veiled - and not so veiled - warnings that any failure to give the president the authority he sought would leave his rivals liable in the event of another terrorist attack.The arguments behind the expanded wiretapping power - that failure to grant it would result in attacks here - were reminiscent of those Republicans aimed at Democrats in the 2002 Congressional election, which brought a Republican victory.