They won’t, the guy’s pretty consistently getting 10% or less in polls of actual Democrats, and his numbers among Dems have been falling in recent weeks as more dirt on him comes to light. The only reason his overall approval ratings aren’t cratering is because his loss of popularity among Democrats is being offset by his gains in popularity among Republicans-- who aren’t going to vote in the Democratic primaries.

Meanwhile, Biden’s been comfortably polling at 60%-plus, even when RFK jr was at the “height” of his popularity among Dems (which, again, was never particularly high).