SECTION 1. Challenging of votes. — (a) Any vote may be challenged for a valid cause by any observer before the voter has deposited his vote in the ballot box.
(b) If a ballot is challenged on valid grounds, the Representation Officer shall segregate it from the unchallenged ballots and seal it in an envelope. The Representation Officer shall indicate on the envelope the name of the challenger and the ground of the challenge.
SECTION 2. Run-off election. — When an election which provides for three (3) or more choices results in no choice receiving a majority of the valid votes cast, and no objections or challenges have been presented which if sustained might change the results, the representation officer shall motu proprio conduct a run-off election within five (5) calendar days from the close of the election between the labor unions receiving the two highest number of votes; Provided, that the total number of votes for all contending unions is at least fifty (50%) percent of the number of votes cast.
The ballots in the run-off election shall provide for two choices receiving the highest and the second highest number of the votes cast.