It sounds like he is conflating the terms "cocktail chatter" and "conventional wisdom". The quoted phrase works equally well with the latter of these terms substituted, viz.
“The sort of conventional wisdom in Washington that, ‘Oh, the [1995-1996] shutdown was a political disaster for Republicans,’ is not borne out by the data.”
"Conventional Wisdom" is the body of ideas or explanations generally accepted as true by the public or by experts in a field. Such ideas or explanations, though widely held, are unexamined. Unqualified societal discourse preserves the status quo.
Cruz essentially blended the two into a neologism; he coined a new phrase. This is supported by the google search for "cocktail chatter wisdom" -cruz, which only turns up one result for me which actually points to Cruz's quote.
Combining the two terms, well, I can't find an authoritative source for the definition of cocktail chatter, but I agree with your rough assessment of the term. Anyways, combining the two terms, the implication is that the idea in question is not only unexamined, it was never critically formed in the first place; rather, this conventional wisdom was just agreed upon by a group of unqualified socialites at a cocktail party.
The further context (or conclusion you, the listener/reader, is expected to draw) of Ted Cruz being a republican legislator operating under a democrat president (Obama), discussing the plans and conduct of a Republican Legislature operating under a Democrat President, is that the government shutdown was a good idea then, produced a successful outcome then, is a good idea now and will produce a successful outcome again.
1995/1996 shutdowns were in the 104th US Congress when both the Senate and Hose of Representatives had Republican majorities for the first time since the 1950s, under Senate Majority Leader Bob Dole and Speaker of the House of Representatives Newt Gingrich. The major difference between the circumstances of that shutdown and this one were that in 1995, the House and Senate passed a spending bill that was vetoed by Bill Clinton, where as in this situation no spending bill could even pass both Chambers of Congress.
My point is that Government shutdowns are infrequent and distinct enough in circumstance that any conventional wisdom one would attempt to draw from them to apply to the future is suspect - it's just going to be different every time. I would say that this drawback applies to Ted Cruz's new term as well.
Additionally, there is a long standing tradition of criticizing everyone in the United States legislature as being an unqualified socialite and, as a result, the entire conduct of Congress is really just a big cocktail party in and of itself. (I gather that British English speakers hold to this tradition as well.)
To summarize: it is a well-known fact that those people who must want to rule people are, ipso facto, those least suited to do it.
To summarize the summary: anyone who is capable of getting themselves made President should on no account be allowed to do the job.
― Douglas Adams, The Restaurant at the End of the Universe
Furthermore, criticizing the correctness of anything within the sphere of "political science", as reported in the news and as practiced by politicians, is pretty much creating a tautology. It is by it's nature inexact and therefore, like economics, almost entirely constructed of conventional wisdom.
I think bib is right on the money by saying Cruz is applying (or trying to apply) sarcasm, but his terms are similar enough that I don't really see the point in his distinction between "cocktail party" and "conventional". Time will tell, however, whether Cruz's coinage will gain currency and circulate.
Disclaimer: I'm a US citizen in Texas, so Ted Cruz is officially my senator.