Let the total number of candidates be x.
Let the number of successful candidates be y.

We are given that the percentage of successful candidates is 75.6%. We can write this as a fraction:
$$y/x = 75.6/100$$

Simplify the fraction:
$$y/x = 756/1000$$

Since we are looking for the least number of candidates, we need to find the smallest possible values for x and y that satisfy the equation. To do this, we can find the greatest common divisor (GCD) of the numerator and denominator of the fraction:
$$\text{GCD}(756, 1000) = 4$$

Divide both the numerator and denominator by the GCD:
$$y/x = (756/4) / (1000/4)$$

$$y/x = 189/250$$

From the simplified fraction, we can see that the least number of candidates (x) is 250, and the least number of successful candidates (y) is 189.

The least possible number of candidates in the examination is 250.