5 – Massachusetts. Romney's time as governor serves simultaneously as his biggest weakness as well as his smallest practical concern. We know as governor, he signed off on a health care overhaul the Democrats basically ripped off and renamed the Patient Protection and Affordable Care Act. And yet, it hasn't hurt him and it certainly hasn't stopped him from criticizing the current law. (Remember he was for an assault weapons ban before he was against it…but maybe flip-flopping's a Bay State pastime.)

The point is, every time the Massachusetts – and its ongoing struggles with health care reform – resurface in the news, as it did earlier this week when the governor signed off on hard spending limits – it's a potential hazard for the presumptive GOP nominee.

4 – The vice-presidential pick. I know political memories can be painfully brief, but it will be a while before anyone forgets what can happen when a candidate taps an unproven, inexperienced governor (or congressman) for a running mate.

3 – Bain. Yeah, yeah, I know, we all thought this had been put to rest, right? Well, the thing is, The New York Times broke a story this week that feds are investigating the hospital chain for fraudulent heart procedures in 2010 – around the same time part-owner Bain Capital looked to boost the company's value in anticipation of an IPO the following year. Of course, by most accounts, Romney had left his post at the company by then, but this story could stir up the Bain hornet's nest all over again.

2 – The Black Swan. This is my stop-gap, wild card pick (and no it's not a Natalie Portman joke either). But maybe some former Bain associate, Olympic official or maybe even Whitey Bulger wannabe step forward with some incriminating story about Romney. Hell, we've already seen bully accusation dropped by former middle school classmates. The press isn't above digging into every dark corner. Again, this doesn't seem terribly likely to me, but I'm hedging my bets at this point.

1 – The tax returns. This has got be the silliest issue in the bunch. But it also stands as the one most likely to blow up the former governor's campaign like an "Oops" moment in a national debate. Even if there's nothing illegal, anything that at hints as blatant tax favoritism reingnites the class debate all over again. And if Ramblin' (Harry) Reid is right and Bain sailed through a decade without dropping so much as a single tax dollar? Fuhgettaboutit.

Don't forget: Next week, we'll look at what's waiting for the president on the tenth calendar page.