What is currently happening in American politics is a matter of positioning.
Trump (the incumbent) is going after Obama in an attempt to reposition the previous administration as corrupt and indecent, in order to extend such a label to the democratic candidate that is going to challenge him in November. Biden (the challenger) is indeed approaching the election with two main topics: “I am not Trump” (not a great idea, by the way, positioning-wise) and “I was part of one of the most successful and popular administrations in the US history” (that in terms of positioning could be seen as a sort of “line-extension”, again not a great idea). And so, Trump is going after Obama to go after Biden, attempting to undermine the image of integrity and likeability the two (but mainly Obama, to be fair) have established.
Now, what Trump is doing is a legitimate strategy. Will it be effective, though? The fragility of the story Trump is building is probably not on his side. You can tell another product is inferior, or has flaws, or is not up to the task, yet that’s not something you can base on hearsay and speculation. Most of all, though, I believe what Trump is doing is not a winning strategy because he has decided to play in the challenger’s field. Instead of leveraging topics that are common to his admistration and to his past success, he is going after something new, a domain (integrity and likeability) that is not really his own.
Curious to see how this will develop in the coming months.