[EM] 50 percent approval.

[Forest Simmons]

Note that if every approval voter approves at least one of the two
front runners, then at least one of them will have 50 percent approval or
more, so it looks like it isn't too far fetched to expect or require 50
percent or better approval for the winner.

Also, optimal zero information strategy tends to give the winner more than
fifty percent approval about fifty percent of the time, given a uniform
distribution of voter utilities for the candidates.

Forest