Learn English – “Spit and baling wire”

From the Online Etymology Dictionary:

Open-and-shut "simple, straightforward" first recorded 1841 in New Orleans.

No further information on the origin of this phrase is available from the other sources I checked.

Open-and-shut is certainly used in the positive sense. In fact, open-and-shut case is a common expression. Two examples:

• An Open-and-Shut Issue on Cruise Ships
• An open-and-shut case
• Golf's host clubs have open-and-shut policies on discrimination

And I also discovered that this phrase (open-and-shut) is extremely popular in golfing circles (think Open) with the hyphens dropped (open and shut or Open and shut). Examples (headlines):

• Some Open and shut Rules cases
• The Open and shut case: Louis Oosthuizen shows the charm of a front-runner...
• It’s an Open and shut case for Gallo
• The gospel according to Gulbis: Open and shut
• Woods wins first Open and Shut Championship

You've pretty much got it with "patchwork or a makeshift measure." A very similar usage of the phrase can be found in a 2008 article from Advertising Age: "Team McCain Reclaims Lead With 'Spit and Glue'". Reading that article might give you a clearer idea of the full meaning of the idiom. You can think of "spit and glue" as "whatever's at hand, though it might not be the ideal or preferred solution."

In the passage you quoted, the full phrase is actually "held together with spit and glue"--it's just confusing because "the fiscal equivalent" intrudes into the middle of the phrase. Something that's held together with spit and glue (or, as Kit mentioned, spit and baling wire) has been patched together to work for the short-term, but it's not very strong or stable, and may not last for long.