CNN asks a very pointed question, Is lying about the reason for a war an impeachable offense?, in a recent article which examines the topic in some detail. Checks and balances, indeed.
The seriousness of the issue is illustrated by this excerpt, comparing this potential scandal to Watergate:
Krugman is right to suggest a possible comparison to Watergate. In the three decades since Watergate, this is the first potential scandal I have seen that could make Watergate pale by comparison. If the Bush Administration intentionally manipulated or misrepresented intelligence to get Congress to authorize, and the public to support, military action to take control of Iraq, then that would be a monstrous misdeed.