Biden certainly comes out of his convention with an advantage on mental fitness. In the Yahoo News/YouGov poll conducted the weekend following the Democratic convention, more registered voters agree that the former Vice President has “the mental ability a president needs” (47%) than say the same for Trump (39%). The difference is bigger on the negative side: Far more reject the notion that Trump is mentally fit (55%) than do the same for Biden (40%).

While Biden has an advantage on this issue, the degree of partisan polarization is striking. Four out of five Democrats (82%) agree that Biden is mentally fit (only 6% disagree), while even more (88%) reject the notion that Trump is mentally fit. Among Republicans, the numbers are essentially reversed – 84 percent consider Trump mentally fit (and 11% disagree), while 81 percent consider Biden unfit.