[Signalman]

Biden’s opponents will jump on this.

[McGruff]

Biden’s opponents will jump on this.

If they don't Trump will. Timing is everything.

[MAGAthon]

neither Fox nor Gateway Pundit mention this part (original source):

27 Feb: Interfax SBI opens case on Biden’s pressure on Shokin – lawyer
Greek law enforcement agencies, in turn, are investigating Shokin’s mercury poisoning in 2019, Teleshetsky said, adding that Shokin himself links this incident to Biden...
Shokin said in late January 2020, that he had survived mercury poisoning in Greece five months before, after which he had to undergo lengthy medical treatment.
https://en.interfax.com.ua/news/general/643674.html

[irishjuggler]

Biden’s opponents will jump on this.

I don't think so The Dem base is heavily invested in the Schiiff/impeachment narrative. Any candidate who jumps on this will be seen as agreeing with Trump that the Bidens did something wrong and/or worth investigating. They can't afford to even concede an inch on this without alienating their looney base.