Don't lie. Don't debate when the facts are in doubt. We have a body of evidence which demonstrates incompetence, incompassion, and deliberate ignorance, so avoid the truly contentious issues. We can rattle all over town about conspiracies here, but the unfettered truth is what wins over the undecided. Make your vocal opponents concede the deliberate obfuscations of these people and that alone destroys their self-assurance:
* The President did not serve honorably in Vietnam. Nor did the Vice President. In fact, a distinct minority of the President's cabinet served in a war in which most were eligible for at a time when military servitude was mandatory and 56,000 Americans lost their lives. Statistically, one in ten who served there was a causalty. There were nearly half a million Americans MEDEVACed to hospitals during the Vietnam war. However, two thirds of all Americans who served in Vietnam volunteered, as did John Kerry. Few (any, besides Powell?) of the Bush cabinet did. With the possible exception of Powell, none have any experience in "assisting" a "sovereign nation" thousands of miles away. Powell may have indirectly helped cover up the My Lai massacre.
sources* The President's economic advisors predicted six million new jobs as a result of the tax cuts they proposed. They lost at least two million jobs. At least three million Americans have lost a job since Bush took office. Some got jobs back, but some fell off the statistical map after their benefits ran out and they stopped reporting attempts to find jobs. The actual unemployment rate may be far worse than announced. There's a pretty decent statistical chance that your idiot Republican friend has lost or been forced out of his or her job in that time, particularly if he or she is not independently wealthy.
* The President has repeatedly mis-labeled his legislative initiatives in an effort to deceive the people. The Healthy Skies Initiative allows certain factories to avoid upgrading to the latest emission standards. The Healthy Forests Initiative gives the go-ahead to cut old-growth trees which can't be replaced in half a millenium.
* The presence of terrorists in Iraq today has everything to do with terrorism today in Iraq; it has nothing to do with support of terrorism in Iraq prior to 9/11. There are also insurgents in Iraq who are not what would normally be called "terrorists," unless you term all insurgents "terrorists." Plenty of them have brand new blood-feuds against Americans who didn't and never would have had such motivation prior to our invasion of their country.
* Even if you believe that Saddam was supporting terrorists, there is not one shred of credible information released which has shown that he was doing it in anything but a monetary or medical fashion, as in checks to the families of suicide bombers in Palestine. If you want to go there, you might like to have your friend check out the similar donors and comfort offered from Egypt, the UAE, Tunisia, Pakistan, and Saudi Arabia, from which nineteen of the twenty terrorists of 9/11 originated.
* If your friend pounds the table and wants to take them all out, you might remind him that eight and three quarters or so of our ten Army divisions are already deployed or preparing to deploy around the world. There is the equivalent of two divisions of combat soldiers who have already been killed or wounded since Bush took office--29,000, last I personally counted (fortunately, most aren't that badly hurt). We're not asking for a significant expansion of the armed forces, because we can't afford it. See the tax cuts to the rich above.
* Those weapons of mass destruction in Iraq were either destroyed before the invasion, hidden and not found, or given to the terrorists themselves. Not one of those major possibilities is a success for the defense of American borders. Mission failed.
Hammer these facts. Well, at this point they're pseudo-facts, since I'm too tired to cite them, but you easily can--and I think the collective weight will tell against our Republican friends. If they are too ideologically entombed to change their vote, at least you can encourage them to sit this one out (a tactic they have regularly employed against us with great success, I might add).
This may be the most important election we see in our lifetimes. Don't let your friends go to the polls without being armed with the truth, as we're allowed to know it.