If the recent exchanges between President Bush, Barack Obama and John McCain on Hamas and terrorism are a preview of the general election, we are in for an ugly six months. Despite his reputation in the media as a charming maverick, McCain has shown that he is also happy to use Nixon-style dirty campaign tactics. By charging recently that Hamas is rooting for an Obama victory, McCain tried to use guilt by association to suggest that Obama is weak on national security and won't stand up to terrorist organizations, or that, as Richard Nixon might have put it, Obama is soft on Israel. President Bush picked up this theme yesterday. Without naming Obama during his speech last night to Israel's Knesset, Bush suggested that Democrats want to "negotiate with terrorists" while Republicans want to fight terrorists. The Obama campaign was right to criticize the president for his remarks and for engaging in partisan politics while overseas. Many presidents have said things abroad that could be construed as violating this unwritten rule of American politics. But it is hard to remember any president abusing the prestige of his office in as crude a way as Bush did yesterday. Charging your opponents with appeasement and likening them to Neville Chamberlain in the Knesset is a brutal blow. It is bad enough that Republicans use the politics of personal destruction here at home, but to deploy that kind of political weapon at an occasion as solemn as an American president addressing the parliament of a friendly government marks a new low. McCain, meanwhile, is guilty of hypocrisy. I am a supporter of Hillary Clinton and believe that she was right to say, about McCain's statement on Hamas, "I don't think that anybody should take that seriously." Unfortunately, the Republicans know that some people will. That's why they say such things. But given his own position on Hamas, McCain is the last politician who should be attacking Obama. Two years ago, just after Hamas won the Palestinian parliamentary elections, I interviewed McCain for the British network Sky News's "World News Tonight" program. Here is the crucial part of our exchange: