"How would a debt default by the federal government impact the home mortgage market?"
We can only guess about the extent of the impact, but it would range somewhere between ugly and catastrophic. Ugly might be a doubling of interest rates and a drop of 50 percent in loan volume. Catastrophic would mean an almost complete shutdown.
About 95 of every 100 home loans being written today are placed into mortgage-backed securities that are sold in the market with guarantees by Fannie Mae, Freddie Mac or Ginnie Mae. These are federal government guarantees, the value of which would drop like a rock with a default.
At best, the securities market would immediately demand a sizable rate premium on new guaranteed mortgage-backed securities to compensate for the added risk. This would immediately translate into sharply higher interest rates charged to new borrowers.
At worst, the markets for these securities would stop functioning altogether as investors retreated to the sidelines to await further information on which government obligations would be honored and which would not. That could be a long wait, as the systems the government uses to make payments have no provisions for allocating funds when there isn’t enough money to pay all claims, and there are no contingency plans for this contingency.
"If a default had the horrendous consequences you describe, and these induce Congress and the Obama administration to agree finally on an increase in the debt ceiling, how long would it take financial markets to return to normal?"
Markets would never return to a state where U.S. government obligations are viewed as riskless. We will pay for this loss of grace forever.
Investors in fixed-income securities are worst-case-oriented, and make a major distinction between the impossible and the unlikely. The current rates that the Treasury must pay investors are based on the assumption that default is impossible. Once a default occurs, it will NEVER again be viewed as impossible. The additional cost of carrying debt on which default is possible will be paid forever.
"How much extra would it cost?"
That is not knowable in advance, but I’ll hazard a guess. My guess is that the cost of carrying the federal debt will increase by about 3 percentage points where it would more or less match the return on investment-grade corporate bonds. On a debt of $14 trillion, an increase of 3 percent in carrying cost would add about $420 billion to our annual deficit.
An optimistic estimate would be that the cost would rise by only 0.25 percent, which would increase the annual deficit by "only" $35 billion.
"Do you really think there will be a default?"
Given the current political impasse, I think the probability is frighteningly high. The message I drew from last night’s address by President Obama, and the follow-up comments of House Speaker John Boehner, is that both were more heavily invested in their positions on spending and taxes than on the need to avert default.
Many important events, especially in the political world, are the result of inadvertence. Nobody planned them and often nobody wants them, but events set in motion years earlier acquire a momentum of their own, and nobody has the motivation and/or power to stop it. Because nobody wants it, everybody expects someone else to swing the axe.
In that connection, the threat posed to mortgage lenders, Realtors and homebuilders by a debt default is enormous. But where are the trade groups? When a bill is introduced to, say, eliminate the mortgage interest deduction, the trade groups are all over the Congress and administration to beat it. But on an issue that threatens their very existence, they are nowhere to be seen. Their assumption seems to be that at the 11th hour, the politicians will prefer doing the right thing to laying the blame for disaster on their adversaries.
In the current political climate, that is a terribly risky assumption.