The longer the Democrat/Left can extend impeachment the less time Sanders and Warren have to campaign, therefore the push to extend impeachment with a feeble call for more and more witnesses (and people like Bolton and Romney are helping them along) will give Biden a significant edge over his communist opponents.
The problem for the Democrat/Left is that Biden would likely be called as a witness ... and the Left knows this (they're already trying -- again, feebly -- to say Biden is not "material" to the impeachment trial and thus cannot be called as a witness ... they'll lose that argument because if anyone is "material" it's the Bidens!)
Biden's testimony (most likely a continuous stream of 5th Amendment refusals to respond) would put Sanders and Warren right back in the fight ... and if Biden prevails then the whacked-out supporters of Sanders and Warren have just another reason to stay home.
It will be interesting how this plays out over the next day or two ...
If Biden WERE called, the MSM would do exactly what they did yesterday to Pam Bondi -— they wouldn’t broadcast it, and half the country would STILL be ignorant of Biden’s criminality. NO WITNESSES!!! The democrats had their chance. The Senate’s job is to decide based on the impeachment case it sent to the Senate.