As long as you've got a good reason, like...say...if the truth might hurt your party:

Bush, Nov. 1:

Q: Assuming their health holds up, do you want Vice President Cheney and Defense Secretary Rumsfeld to be with you until the end?

Bush: Yes, I am.

Bush, Nov. 8: 

Q: Last week you told us that Secretary Rumsfeld will be staying on. Why is the timing right now for this, and how much does it have to do with the election results?

Bush: Right. No, you and Hunt and Keil came in the Oval Office, and Hunt asked me the question one week before the campaign, and basically it was, `Are you going to do something about Rumsfeld and the vice president?' And my answer was, `They're going to stay on.' And the reason why is I didn't want to inject a major decision about this war in the final days of a campaign. And so the only way to answer that question and to get you on to another question was to give you that answer.

(Bush went on to say that at the time he also had not had a chance to visit with Robert Gates, his nominee to take over at the Pentagon, and had not yet had a final conversation with Rumsfeld.) 

If his lips are moving, he's lying - but he's got good reason!