I like the spirit of what you're saying, but I'm not convinced that you've made a rational argument for it. Also, I'm concerned that you might have started with the conclusion that a rational argument must flow forward and constructed an account to justify it. If so, in your terms, though not in mine, that would make your conclusion irrational.
I think it can be perfectly rational to think backwards from any conclusion you want to any explanation that fits. Rationality is among other things about being bound by the requirement of consistency in reasoning. It's about creating an account from the evidence. But it's also about evaluating evidence, and that part is where it gets problematic.
In an open and complex world like the one we live in every day, weighing evidence is largely a non-rational (para-rational? quasi-rational?) process. We are operating only with bounded rationality and collections of murky impressions. So, your idea of making a checklist and somehow discovering who the best candidate is is already doomed. There is no truly evidence-driven way of doing that, because evidence does not drive reasoning-- it's our BELIEFS about evidence that drive reasoning. Our beliefs are mostly not a product of a rational process.
A logical explanation is one that follows from premises to conclusions without violating any rule of logic. Additionally, all logical explanations of real world situations involves a claim that the logical model we put forward corresponds usefully to the state of the real world. What we called a "cat" in our reasoning corresponded to that furry thing we understand as a cat, etc. If I can think backwards from a conclusion without finding an absurd premise, then I have a logical explanation. (It may be wrong, of course.)
To attack my self-consistent, logical account of a situation that suggests that X is TRUE, based solely on the fact that I was looking for evidence that X is true, is equivalent to an ad hominem fallacy. I think you can certainly suspect that my argument is weak, and it probably is, but you can't credibly attack my sound argument simply because you don't like me, or you don't like my method of arriving at my sound argument. A lot of science would have to be thrown out if a scientist wasn't allowed to search for evidence to support something he hoped would be true. Also, as you know, many theorems have been proven using backward reasoning.
If you want to attack the argument, you can attack it rationally by offering counter-evidence, or an alternative reasoning that is more consistent with more reliable facts. Furthermore, our entire legal system is built on the idea that two opposing sides in a dispute, marshaling the best stories they can marshal, will provide judges and juries with a good basis on which to decide the dispute.
Instead of calling it irrational, I would say that it's a generally self-deceptive practice to start from a conclusion and work backward. I don't trust that process, but I couldn't disqualify an argument solely on those grounds.
Instead of prescribing forward reasoning only, I would prescribe self-critical thinking and de-biasing strategies.
(BTW, one of the reasons I don't vote is that I am confident that I cannot, under any circumstances, EVER, have sufficient and reliable information about the candidates to allow me to make a good decision. So, I believe all voting decisions people actually make are irrational.)
What you need to remember is that all of this applies to probabilistic arguments with probabilistic results - of course deductive reasoning can be done backward. However, when evidence is presented as contribution to a belief, omitting some (as you will, inevitably, when reasoning backward) disentangles the ultimate belief from the object thereof. If some evidence doesn't contribute, the (probabilistic) belief can't reflect reality. You seem to conceptualize arguments as requiring the outcome if they're valid and their premises are true, which doesn't describe the vast majority.
You are, by occupation, a campaign manager, and you’ve just been hired by Mortimer Q. Snodgrass, the Green candidate for Mayor of Hadleyburg. As a campaign manager reading a book on rationality, one question lies foremost on your mind: “How can I construct an impeccable rational argument that Mortimer Q. Snodgrass is the best candidate for Mayor of Hadleyburg?”
Sorry. It can’t be done.
“What?” you cry. “But what if I use only valid support to construct my structure of reason? What if every fact I cite is true to the best of my knowledge, and relevant evidence under Bayes’s Rule?”1
Sorry. It still can’t be done. You defeated yourself the instant you specified your argument’s conclusion in advance.
This year, the Hadleyburg Trumpet sent out a 16-item questionnaire to all mayoral candidates, with questions like “Can you paint with all the colors of the wind?” and “Did you inhale?” Alas, the Trumpet’s offices are destroyed by a meteorite before publication. It’s a pity, since your own candidate, Mortimer Q. Snodgrass, compares well to his opponents on 15 out of 16 questions. The only sticking point was Question 11, “Are you now, or have you ever been, a supervillain?”
So you are tempted to publish the questionnaire as part of your own campaign literature . . . with the 11th question omitted, of course.
Which crosses the line between rationality and rationalization. It is no longer possible for the voters to condition on the facts alone; they must condition on the additional fact of their presentation, and infer the existence of hidden evidence.
Indeed, you crossed the line at the point where you considered whether the questionnaire was favorable or unfavorable to your candidate, before deciding whether to publish it. “What!” you cry. “A campaign should publish facts unfavorable to their candidate?” But put yourself in the shoes of a voter, still trying to select a candidate—why would you censor useful information? You wouldn’t, if you were genuinely curious. If you were flowing forward from the evidence to an unknown choice of candidate, rather than flowing backward from a fixed candidate to determine the arguments.
A “logical” argument is one that follows from its premises. Thus the following argument is illogical:
This syllogism is not rescued from illogic by the truth of its premises or even the truth of its conclusion. It is worth distinguishing logical deductions from illogical ones, and to refuse to excuse them even if their conclusions happen to be true. For one thing, the distinction may affect how we revise our beliefs in light of future evidence. For another, sloppiness is habit-forming.
Above all, the syllogism fails to state the real explanation. Maybe all squares are rectangles, but, if so, it’s not because they are both quadrilaterals. You might call it a hypocritical syllogism—one with a disconnect between its stated reasons and real reasons.
If you really want to present an honest, rational argument for your candidate, in a political campaign, there is only one way to do it:
Only in this way can you offer a rational chain of argument, one whose bottom line was written flowing forward from the lines above it. Whatever actually decides your bottom line is the only thing you can honestly write on the lines above.
1See “What Is Evidence?” in Map and Territory.