I was shot down on my previous concern troll thread about this. I'm not sure this holds for two reasons.
1) Are we certain that the whole "incumbency" advantage counts when the opponent has served the immediate term before this. I'm thinking most voters view both as having whatever advantages come from incumbency. Certainly, the only historical example, Grover Cleveland v. Benjamin Harrison (1892) proves the exact opposite. Incumbent Cleveland loses to Harrison (1888), and then beats the shit out of Harrison in the 1892 election. So literally the ONLY similar situation we can look at historically is that immediate incumbency didn't help Harrison.
2) Although Harrison looked old as shit, he and Cleveland were both hovering about 60. But note that Harrison's wife died right before the election.
And this interesting wiki tidbit: The tariff issue dominated this rather lackluster campaign. Harrison defended the protectionist McKinley Tariff passed during his term. For his part, Cleveland assured voters that he opposed absolute free trade and would continue his campaign for a reduction in the tariff. Cleveland also denounced the Lodge Bill, a voting rights bill that sought to protect the rights of African American voters in the South.[23] William McKinley campaigned extensively for Harrison, setting the stage for his own run four years later.
I don't think the electorate is astute enough to get past Biden's softer speaking style and remnants of stutter to get to the substance of what the guys are saying. To them, the loud lunatic "seems" younger than soft spoken intellect.