The State of the Union doesn't usually affect the president's approval rating
Biden and Democrats might be hoping that Tuesday night's State of the Union address will give him a political boost, but history shows that's unlikely to be the case.
When we compare Gallup polls taken just before State of the Union addresses since 1978 to Gallup polls taken just after them, we see that the president's approval rating typically doesn't move very much.
On average, a president's approval rating shifts by just 2.6 points after State of the Union addresses. But that shift is just as likely to be negative as it is positive. As a result, the average president has gotten just 0.4 points more popular after the State of the Union.
While a few presidents, such as Bill Clinton in 1998, have emerged from the speech in a significantly improved position, they are the exception, not the rule. And those changes may not even be attributable to the State of the Union; for example, then-President Donald Trump's approval rating rose 6 points after his 2019 address -- but the 2018-19 government shutdown came to an end just a few days before his speech.
-FiveThirtyEight's Nathaniel Rakich