The Globe and Mail reports in its Thursday edition that the potential return of Donald Trump is bamboozling most thinking, particularly overseas, about what might happen next. A Reuters dispatch to The Globe reports that Goldman Sachs on Tuesday said rising Treasury borrowing costs and discord in Congress have raised renewed questions about U.S. debt sustainability -- lifting its assumption of interest expense on government debt to 3 per cent of national output by 2024 and 4 per cent by 2030, surpassing the early 1990s peak by 2025. On that basis, Goldman Sachs increased its 2024 budget deficit forecast out to 2025 by $100-billion (U.S.) to $1.9-trillion (U.S.) -- or 6.5 per cent of GDP. Goldman, however, pointed out that when debt servicing costs spiked like this in the 1980s, government shrank the primary deficit, which excludes interest expense, to offset it. A fiscal adjustment akin to the one enacted in 1993 would be enough to do that again over five years. On current poll readings at least, next year's election will do nothing to end the fiscal war. For investors grappling with long-term bond yield uncertainty and a re-emerging risk premium embedded in them, the picture looks unnerving to say the least.