It is desperation, but I don’t think it relates to Trump at all; they’re circling the Dem establishment wagons to deal with the RFK insurgency - as they believe his Veep pick showed he’s the flaming lib in the race, without Biden’s corruption or racism.
Prior to his VP pick, there was debate about which candidate would be worse impacted by JFK’s candidacy; since then, there has been no discussion (and the ex-presidents showed up in NYC together).
Well, maybe not reaking of desperation. It depicts 3 rather useless presidents as a reason to vote for one good one.