We cannot directly observe what would have happened if the U.S. presidential election had been held on July 11, 2020, so the prediction describes a counterfactual scenario whose truth can’t be definitively verified.

However, available evidence from that time mostly supports the direction of Friedberg’s claim:

• National polling averages: An Inside Elections "Snapshot" as of July 10, 2020 found Joe Biden leading Donald Trump nationally by about 8 points on average (47.7% to 39.7%) based on 14 national polls over the prior two weeks, and also ahead in key battleground states. (insideelections.com)
• Individual national polls: An NBC News/Wall Street Journal poll conducted in mid-July 2020 (field dates July 9–12) showed Biden leading Trump 51%–40% among registered voters, well outside the margin of error. (cnbc.com)
• Swing‑state polling: A CNBC/Change Research swing‑state survey taken in mid‑July (field dates that same weekend) showed Biden ahead in each of six critical battleground states (AZ, FL, MI, NC, PA, WI) and leading 49%–43% across those states combined, with a concurrent national poll showing Biden up 51%–41%. (cnbc.com)
• Betting/market odds: By early July 2020, major betting markets had shifted to make Biden a clear favorite: for example, one aggregated line on July 1 listed Biden as roughly a –166 favorite over Trump (implied probability above 60%). (sportsbettingdime.com)
• Eventual November result: When the election was actually held on November 3, 2020, Biden did defeat Trump, winning 306 Electoral College votes to Trump’s 232 and about 51.3% of the popular vote to Trump’s 46.8%. (en.wikipedia.org)

These data points strongly suggest that, had an election been held around July 11, 2020, Biden was more likely than not to win. But because no election took place on that date, the categorical statement “if the vote were to happen today, Joe Biden would win” cannot be conclusively proven or falsified. Therefore the appropriate classification is ambiguous rather than clearly right or wrong.