The United States presidential election will be held on November 5. In analyst Nate Silver’s aggregate of national polls, Democrat Kamala Harris leads Republican Donald Trump by 49.3-46.5, a slight gain for Trump since last Monday, when Harris led by 49.3-46.2.

Joe Biden’s final position before his withdrawal as Democratic candidate on July 21 was a national poll deficit against Trump of 45.2-41.2.

The US president isn’t elected by the national popular vote, but by the Electoral College, in which each state receives electoral votes equal to its federal House seats (population based) and senators (always two). Almost all states award their electoral votes as winner-takes-all, and it takes 270 electoral votes to win (out of 538 total).

Relative to the national popular vote, the Electoral College is biased to Trump, with Harris needing at least a two-point popular vote win to be the Electoral College favourite in Silver’s model.

Last Monday, Harris led by one to two points in Pennsylvania (19 electoral votes), Michigan (15), Wisconsin (10) and Nevada (six). In the last week, Trump has gained in all these states in Silver’s aggregates, reducing Harris’s lead to about one point in these states.

If Harris wins these four states, she probably wins the Electoral College by at least a 276-262 margin. Trump leads by less than one point in Georgia and North Carolina, which both have 16 electoral votes.

While Harris is still barely ahead in the Electoral College, her margins have been reduced in the states where she’s leading. As a result, Silver’s model now gives Harris a 52% chance to win the Electoral College, down from 56% last Monday.

This means the presidential election is effectively a 50-50 toss-up. There’s a 23% chance that Harris wins the popular vote but loses the Electoral College. The FiveThirtyEight model is giving similar results to Silver’s model, with Harris a 53% favourite.

There’s still over three weeks until the election, and polls could change in that time. The polls could also be biased against either Trump or Harris, and in this case that candidate could win easily. With the polls across the swing states so close, either candidate could sweep all these states.

I wrote about the US election for The Poll Bludger last Thursday, and also covered the UK Conservative leadership election, the far-right winning the most seats at the September 29 Austrian election and Japan’s October 27 election.

Ratings, economic data

Harris’s net favourability peaked about two weeks ago at +1.4 in the FiveThirtyEight national poll aggregate, but it has now dropped back to net zero, with 46.8% favourable and 46.8% unfavourable. Harris’ net favourability had surged from about -16 after becoming the Democratic nominee, and she gained further ground after the September 10 debate with Trump.

Trump’s net favourability has been steady in the last two months, and he’s now at -9.4, with 52.6% unfavourable and 43.2% favourable. Harris’ running mate Tim Walz is at +4.2 net favourable and Trump’s running mate JD Vance is at -9.6 net favourable. Biden’s net approval remains poor at -14.0.

US headline inflation rose 0.2% in September, the same increase as in August. In the 12 months to September, inflation was up 2.4%, the smallest increase since 2021. Core inflation increased 0.3% in September, the same as in August, and is up 3.3% in the 12 months to September.

Real (inflation-adjusted) hourly earnings were up 0.2% in September after a 0.3% increase in August, while real weekly earnings slid 0.1% after a 0.6% increase in August owing to changes in hours worked. In the 12 months to September, real hourly earnings were up 1.5% and weekly earnings up 0.9%.

Congressional elections

I wrote about the elections for the House of Representatives and Senate that will be held concurrently with the presidential election three weeks ago. The House has 435 single-member seats that are apportioned to states on a population basis, while there are two senators for each of the 50 states.

The House only has a two-year term, so the last House election was at the 2022 midterm elections, when Republicans won the House by 222–213 over Democrats. The FiveThirtyEight aggregate of polls of the national House race gives Democrats a 47.1–45.9 lead over Republicans, a gain for Republican from a 46.7–44.5 Democratic lead three weeks ago.

Senators have six-year terms, with one-third up for election every two years. Democrats and aligned independents currently have a 51-49 Senate majority, but they are defending 23 of the 33 regular seats up, including seats in three states Trump won easily in both 2016 and 2020: West Virginia, Montana and Ohio.

West Virginia is a certain Republican gain after the retirement of former Democratic (now independent) Senator Joe Manchin at this election. Republicans have taken a 5.4-point lead in Montana in the FiveThirtyEight poll aggregate, while Democrats are just 2.3 points ahead in Ohio.

Republicans are being challenged by independent Dan Osborn in Nebraska, and he trails Republican Deb Fischer by just 1.5 points. Democrats did not contest to avoid splitting the vote. In other Senate contests, the incumbent party is at least four points ahead.

If Republicans gain West Virginia and Montana, but lose Nebraska to Osborn, and no other seats change hands, Republicans would have a 50-49 lead in the Senate. If Harris wins the presidency, Osborn would be the decisive vote as a Senate tie can be broken by the vice president, who would be Walz. This is the rosiest plausible scenario for Democrats.

Adrian Beaumont is Election Analyst (Psephologist) at The Conversation; and Honorary Associate, School of Mathematics and Statistics, The University of Melbourne.

This article was first published on The Conversation.