The claim is about a counterfactual: “if the election were today [June 20, 2020], he would lose.” The presidential election was actually held on November 3, 2020, not June 20, so we have no direct empirical result for that specific date.

What we can say is that polling around June 20, 2020 strongly indicated Joe Biden was ahead:

• A CNBC/Change Research poll conducted June 12–14, 2020 found Biden leading Trump by 10 points nationally and by 3 points across six key battleground states (Arizona, Florida, Michigan, North Carolina, Pennsylvania, Wisconsin).(cnbc.com)
• Around early June 2020, RealClearPolitics’ national polling average had Biden up by about 7.8 percentage points over Trump.(cnbc.com)
• FiveThirtyEight’s early general-election polling averages (launched in June 2020) similarly showed Biden with roughly a 9-point national lead and advantages in most major swing states.(fivethirtyeight.com)

These data make it likely that, had an election been held that day and votes mirrored the polling, Trump would have lost. However, polling is probabilistic, the Electoral College can diverge from the popular vote, and no actual election occurred on June 20. Because the statement concerns a hypothetical event that never happened, it cannot be definitively verified or falsified, even though available evidence supports its direction. Hence the prediction is best classified as ambiguous, not strictly right or wrong.