A few points.

1. Capture the applause with the microphone input of the sound card.
2. Place the microphone far from the audience. Sound intensity follows an inverse-square law. If the mike is close to one candidate's family, she'll win.
3. Use PDL and PDL::Audio to analyze the audio. You probably want either the peak power or the integral of the power spectrum.

To minimise favouring any particular audience member the audio source (microphone) or sources must be located a good distance from the entire audience (maybe a rooftop) in an attempt to make the average distance to each audience member proportionally similar.

Then, peak audio response, could potentially be done by sampling input wave forms and measuring average audio response over a given time period. Because it's total audience energy you're looking for, not just a peak sample that happened to occur at some point in time.

I think you'd do better with an integrated value - the magnitude of the signal summed over the duration. Otherwise a single loud clap would register higher than sustained, less noisy applause that went on for many minutes.

Assuming you have some sort of analog to digital conversion available, this should require little more than sampling the value at regular intervals and summing.