I think the biggest risk is recession, not financial crisis

So on August 2, if no deal has been reached to lift the debt ceiling, the US government has to start deciding which bills to pay and which to delay or renege on. My guess is that the Treasury will announce unequivocally that it will honor the debt. Otherwise there will be another financial collapse and horrible recession. The long term consequences for the terms on which the US can borrow and the role of the dollar as the world's main reserve currency would also be severe. I'd also expect the Federal Reserve to buy US government securities in whatever amounts are needed to prevent a major spike in interest rates.

Consequently, I think the main danger posed by a funding crisis is what happens if the Treasury stops making payments to other claimants on the government budget -- Social Security checks, reimbursements to doctors and hospitals for Medicare and Medicaid, payments to government contractors, etc. The total impact is estimated to be about 10 percent of GDP -- enough to throw the economy into another major recession. Of course, that is also about what the effect would be of a resolution of the crisis on Republican terms.