How a presidential debate moves the bond market

Joe Biden's performance in the 27 June presidential debate against Donald Trump moved markets as well as voters. Betting odds swung sharply toward a Republican sweep after the president's halting showing, and the whole US Treasury curve reacted at once.

Long bonds take the hit

Bond traders quickly priced in what a second Trump term might mean for the economy, chiefly universal import tariffs and a federal deficit swollen by more tax cuts. Long-dated Treasury yields jumped as term premia widened sharply, while expectations for short-term rates barely moved. For now, long-dated Treasuries are the market's main way of pricing American political risk.

How an event study reads it

Economists who want to isolate the effect of a single event look at a narrow window around it and compare prices just before and just after. The debate was a clean case. It started in the evening, after the cash market had closed, and nothing else of importance happened overnight, so the move in futures and in Asian trading can be attributed with some confidence to the change in perceived election odds. The morning's data, including the May figure for core personal consumption expenditures inflation at 2.6 per cent, the lowest in more than three years, pointed the other way and should have pulled yields down.

That the long end still sold off is the telling detail. Soft inflation data would normally lower yields across the curve by raising the odds of Fed cuts. Instead the curve steepened: two-year yields, which track expected policy rates, held close to their levels, while ten- and thirty-year yields rose. The market was not revising its view of the Fed. It was demanding more compensation for holding long-dated debt through a period of fiscal and trade uncertainty.

Why tariffs and deficits hit the long end

The two policies work through different channels. Tariffs raise import prices directly, and a broad tariff on all imports would lift the price level in a way that the Fed might have to respond to if it spilled into expectations. That risk shows up as a higher inflation premium in long-dated bonds. Tax cuts financed by borrowing increase the supply of Treasuries, and investors need a higher yield to absorb it, especially with the Fed still shrinking its balance sheet.

The fiscal backdrop makes the second channel sharper than it was eight years ago. The Congressional Budget Office raised its estimate for this year's deficit to $1.9 trillion earlier this month, with the economy near full employment. The individual tax cuts passed in 2017 lapse by the end of 2025, and extending them would add substantially to borrowing. A government with unified control of Congress would find that far easier to do, which is why the odds of a sweep, rather than of a Trump win alone, moved the market.

The 2016 template

Traders had a precedent in mind. After Trump's victory in November 2016, the ten-year yield rose by more than half a percentage point within weeks as markets priced tax cuts, infrastructure spending and faster growth. The dollar strengthened, bank shares rallied and emerging-market currencies fell. The debate move was a small version of the same "Trump trade", built on the same expectation of looser fiscal policy.

The differences matter, though. In 2016 the ten-year yield started below 2 per cent, inflation was below target and the federal deficit was much smaller as a share of output. Today yields are above 4 per cent, inflation has only recently cooled, and debt held by the public is far higher. A second fiscal expansion would start from a weaker position, which is why some investors think the bond market's reaction could be larger this time rather than smaller.

Winners and losers of the repricing

A steeper curve helps banks, which borrow short and lend long, and it has been a long wait for them since the curve inverted in July 2022. It hurts holders of long-dated Treasuries and anyone whose borrowing costs follow them, above all mortgage borrowers, since thirty-year mortgage rates track the ten-year yield. Companies that rely on imported components, and the countries that export them, face the tariff risk directly, and currencies such as the Mexican peso and the Chinese yuan are exposed to any hardening of trade policy.

The case for caution

One debate is a noisy signal. The election is more than four months away, and polls, not betting markets, will guide the campaigns. Democratic commentators began questioning within hours whether Biden should remain the nominee, and a change of candidate would unsettle the odds that the market has just priced. Campaign pledges also have a habit of shrinking once they meet Congress and the constraints of the bond market itself. A move of a few basis points on one night is a reading of sentiment rather than a forecast of policy.

The move also coincides with other forces pushing long yields up, including heavy Treasury issuance and a gradual recovery in the term premium that began last year. Separating the political component from those trends becomes harder the further the window extends beyond the debate itself. Event studies are most reliable over hours, and least reliable over the weeks in which a campaign actually unfolds, so the overnight move is the cleanest estimate the market will get of how much a Republican sweep is worth to bond investors.

What to watch through the summer

The Republican convention in Milwaukee in mid-July and the Democratic convention in Chicago in August will reset the odds, as will any decision on the Democratic ticket. The Treasury's quarterly refunding at the end of July will show how much long-dated debt the market has to absorb. Polls in the swing states, and the gap between two- and ten-year yields, are the simplest gauges of how much political risk the market is carrying.

The debate showed that the bond market is now pricing the election as well as the economic data. If Trump's lead holds, long-dated yields will probably keep rising through the campaign as investors demand more to hold the extra debt. Mortgage borrowers and the Treasury itself are the most exposed, and the yield curve is likely to keep steepening into November, even if the Fed cuts in the autumn.