One of the most practical reasons to persue impeachment and conviction for both Cheney and Bush is that they are still dangerous. Impeachment and conviction should be considered an urgent matter of national security.
Duh!
They lied to start one botched war with Iraq, and for that they deserve to have the case vigorously brought against them. The decision by Pelosi to deliberately let Bush off the hook for that High Crime was absolutely the wrong decision. After lying to start one war and getting away with it, what guarantee do we have that Bush-Cheney won't do it again? None.
The Iran NIE shows that they have been flat out lying with their belicose Iran hype, just like Iraq in 2002-2003.
Impeach and convict them for what they have done.
But also impeach and convict them to prevent the damage that they can still do.
Keep going for more discussion.
The opponents of impeachment say it is not practical. But a successful impeachment might prevent Bush and Cheney from creating another major national security disaster. It might save tens of thousands of lives. It would definitely begin to restore our credibility around the world. It would help restore the Constitution that so many have taken an oath to protect.
If Bush and Cheney were thrown out of office in say, 5 months from now, we could start ending the Iraq war 5 months from now, rather than waiting around until January of 2009. That seems very practical to me, and a worthy goal to try to accomplish. As it stands right now, Commander Veto and the obstructionist Republicans in the Senate are making sure that the Democrats cannot accomplish much of anything. Persuing the impeachment and conviction of Bush and Cheney would be a much more "real" accomplishment in my view.
The opponents of impeachment don't deny that the case for impeachment is strong. Between lying to start a botched war, and numerous substantial violations of the Constitution, the case for impeachment is solid. But how to get 17 18 Senate Republicans (and Lieberman) to vote for a conviction? Well, I think if Congress were to show a thorogh presentation of the evidence to the American people, in high profile hearings, with all the whistle blowers, documents, and evidence from A to Z, you would be able to put the Republicans in a very tough situation.
The question for members of the Senate would be: "Do you support the Bush-Cheney decision to lie to start a war, and use the state of war to repeatedly violate the Constitution?"
Another tough question to put to Senate Republicans is "Do you think the troops deserve justice, or do you think Bush-Cheney should get away with it?"
There are a multitude of possibilities. Here's another one: "Do you believe war criminals should be in command of the world's most powerful military?" Or how about "Should our troops have to take orders from war criminals?" These just roll of the tongue. "Would you have supported former President Clinton if he decided to lie to start a war, even though you thought he should be impeached for lying to a grand jury?" Or this rhetorical zinger: "Do you stand with the 100% of Americans who were lied to about the reasons for war, or do you stand with the President?" Democrats would have the political benefit of showing that a Republican President lied to start a war, and the Republican Congress would not expose it. If your concern is more about politics, rather than what is practical, would could be better for Democrats than to really, actually hold Bush accountable? The current approach of letting Bush-Cheney get away with the High Crimes certainly isn't winning much support from the public.
At that point, it is still possible that a Senate conviction would fail, but the Republicans would have an electoral blood bath of epic proportions if they stood by a President who lied to start a war. If the Democrats were to hold the necessary hearings, we might not even get to the point of a vote in the Senate. Perhaps a group of Republican Senators would beg Bush and Cheney to step down, not because it's the right thing to do, but because they need to save their own asses.
Back to the Iran NIE.
They are doing it again. They've obviously been trying to make the case for an attack on Iran, despite the fact that Iran is not an imminent threat. And despite the publication of the Iran NIE, Bush-Cheney will not stop. Remember how persistent they were with Iraq? They ignored all the good inteligence that Iraq had no recent WMDs. They promoted or even manufactured fake evidence of WMDs. They lied about ties between Saddam's Iraq and Al Qaeda. They lied about aluminum tubes, mobile weapons labs, and nuclear weapons. Bush was even willing to commit specific crimes, such as lying to a joint session of Congress during his 2003 State of the Union address. It didn't matter to Bush-Cheney that it was not in our nation's best interest to go to war. They were persistent, they got the war they wanted, and (so far) they are getting away with the High Crime of lying to start a war.
The same will apply with Iran. The latest fiasco with the NIE is just a temporary setback. They will manufacture the case for an attack on Iran if we choose to deliberately let them off the hook. Did you ever here of the USS Maddox and the Gulf of Tonkin?
The only practical way to ensure that Bush and Cheney are no longer dangerous to us and the world is to force them out of office. As soon as possible.
There are two possibilities for the line of succession. In one scenario, Nancy Pelosi is elevated to the office of President. That would likely not be palatable to a lot of Republicans, so we could promote the Nixon-like exit. First force out Cheney. Bush could appoint a new VP that would need the approval of a Democratically controlled House and Senate, so even there we could block the appointment of a hardcore winger. If Bush threatened to appoint an extremist as his new VP, we can threaten back with the notion of "President Pelosi".