As I understand it, the Prez and other politicans are for this for 2 reasons:
This is our chance to save the R party from itself, I think.
If left to their own devices, the Ds will take Congress. If we agree that Congress needs a wholesale change, but insist on replacing republicans with better republicans, we can save the day.
That may be true, regardless of security risks--but they won't be voting in this election. Nothing moves that fast in government.