At least three indicators Arbeter follows indicate the 2013 rally has moved too sharply to the upside without a meaningful break.
Combined with a head-and-shoulders formation on the S&P 500 chart, market behavior looks a lot like it did in late 2010 and early 2011, conditions that led to a sharp market decline that Arbeter thinks could hit 12 percent.
That would take the stock index closer to the 1,530 neighborhood.
In order to resist that type of decline, the market will have to resist the pressure of conflicting economic signals.
Just as it looked like growth was hitting sustainable levels, a batch of indicators last week indicated much work needs to be done.
Of the 22 data releases over the period, 16 came in weaker than forecasts while only four registered positive surprises, according to Bespoke Investment Group.
(Read more: 'Dr. Doom' Roubini makes case FOR the US economy)
In fact, the government shutdown may be the least of the market's worries.
The bulls at Piper Jaffray predicted "this turbulence could be a buying opportunity," while John Stoltzfus, chief market strategist at Oppenheimer, pointed out that the market actually rose 1.83 percent and 0.06 percent respectively during the last two shutdowns.
Stoltzfus expects that "even if legislators in Washington fail to come to an agreement over the issues in time to avert a partial government shutdown, it won't be long before legislators on both sides of the aisle feel enough heat from the disapproval and pain felt by the majority of their respective constituencies to make the tenure of any shutdown short."
_ By CNBC's Jeff Cox. Follow him @JeffCoxCNBCcom on Twitter.