WASHINGTON, May 18 — The ferocity of the White House counterattack this week, when confronted by criticism that President Bush and his top advisers knew more than the public about hijacking threats before Sept. 11, is a sure sign that they recognize the political danger should Democrats press the issue through the coming election campaign. Mr. Bush's political team appeared to sense that taking the question to the voters might backfire on the Democrats, with the president, and by implication his party, suffering no lasting political damage from the disclosures of the past week. The central question is where the...