Never a right time. My concern is during such a dangerous and fatal time, you cant have a leader who by the day, the public is growing increasingly angry with. It will lead to public discontent which will lead to a public defiance. Exactly what we dont want. Im not even saying that its just or particularly fair, but in such times, you cant afford a public defiantly against you whilst trying to caution, control and enforce measures.
The maths will not work. It just may be needed. Not that it would make a huge difference in policy or action but its about getting the public to do the right thing. You lose belief, the less likely you are to adopt severe personal measues and sacrifices that are being asked for.