Considering these people rarely take time out of their schedule to vote on an issue in the Senate, unless it pertains to a hot-button issue in the presidential campaign, I see no reason why they should stay in office. They are elected to represent their state's best interests, but if they are not working in the interest of the state then why should they continue to hold a seat which is all but vacant? They need to at least step aside while they are running a national campaign and let someone assume their duties temporarily. Especially when you consider the type of issues we face here domestically today, such as energy crises, economic downfall and the war in Iraq. Illinois and Arizona are two of this country's biggest states, both states are being crippled by the economy's downward slope and neither candidate is in the Senate trying to alleviate the pain of their constituents. They are not doing what they were elected to do.
As much as Bob Dole annoys the hell out of me, I can at least give him credit for stepping aside when he ran for President... and he was Senate Majority Leader, a post he could have kept for years had he stayed on...