The careful balancing act that either of these theories implies risks not just Pres. Bush's re-election, but the popular base of support for the war -- both the war on Iraq and the Bush strategy for the war on al-Qaeda.
Why would Pres. Bush have missed an opportunity to galvanize public support for the war on Iraq by stating publicly the reasons which he ostensibly already knows? This isn't just a question of re-election strategy: the successful prosecution of the war is at risk precisely because much of the U.S. public is uncertain why we are at war with Iraq and thinks it may be needless.
The tactic of intentionally waiting until just before the election would be likely to backfire. It will be attributed to political opportunism by much of the public, and many people who would have believed it earlier simply won't believe it at that point. Combine that with the fact that there appear to be moles in the government who are willing to publish "tell-all" books to the detriment of the administration, and there's a good chance that the tactic wouldn't even be kept secret.
Now, maybe one of these theories really is right. If so, it's a poor tactical choice on the part of the Bush administration.
I'm more inclined to think that neither of these theories is the reason. Either there's some other reason that's keeping Pres. Bush from revealing the Iraq-al Qaeda connection, or else the connection is minimal and there's not much to reveal.
After all, both raw intelligence and its interpretation are full of errors and uncertainties, and even disinformation. The President hears "There is a connection" from one advisor, "There's not a connection" from another advisor, and "We don't know" from a third advisor.
Maybe Pres. Bush is, very reasonably, unwilling to go out on a limb in such a situation.