Unless Congress acts, the U.S. government will hit its $16.7 trillion borrowing limit by mid-October. That’s the latest estimate from Treasury Secretary Jack Lew, delivered in a letter Monday to House Speaker John Boehner, R-Ohio. Coupled with the Sept. 30 expiration of the government’s authority to spend money on discretionary programs, Lew’s letter sets the stage for yet another round of Washington’s endless partisan wrangling over fiscal policy.

To date, no combination of policy necessity and deadline pressure has sufficed to force a “grand bargain” that would address the country’s long-term budgetary imbalances. Will the latest threats — a partial government shutdown if there’s no new spending bill; an even more damaging default if the debt ceiling isn’t raised — induce any better outcome in the handful of legislative days available after Congress reconvenes Sept. 9?

In some ways, the impasse has worsened since Congress and President Obama cobbled together a temporary fix to the “fiscal cliff” drama nine months ago. A promising series of meetings between Obama and a group of compromise-minded Republican senators fizzled. Sen. Ted Cruz of Texas and others on the Republican right launched a deeply mischievous campaign to “defund” Obamacare — even if that means shutting down the government.

The broad outlines of a grand bargain are known to all: trims to Social Security and Medicare, combined with revenue-enhancing tax reform sufficient to set the federal deficit on a declining path in the medium to long term.

The sacrifice would be real but, for most Americans, modest, and certainly more modest than what later generations may face if we do nothing. So far, neither congressional Republicans nor President Obama has been willing to embrace this truth and act on it. They still have a chance to change this fall, if they choose to take it.