The advent of space-based photometry provides the opportunity for the first precise characterizations of variability in Mercury-Manganese ( HgMn/CP3 ) stars , which might advance our understanding of their internal structure . We have carried out a spectroscopic and photometric investigation of the candidate CP3 star KIC 6128830 . A detailed abundance analysis based on newly-acquired high-resolution spectra was performed , which confirms that the star ’ s abundance pattern is fully consistent with its proposed classification . Photometric variability was investigated using four years of archival Kepler data . In agreement with results from the literature , we have identified a single significant and independent frequency f _ { 1 } = 0.2065424 d ^ { -1 } with a peak-to-peak amplitude of \sim 3.4 mmag and harmonic frequencies up to 5 f _ { 1 } . Drawing on the predictions of state-of-the-art pulsation models and information on evolutionary status , we discuss the origin of the observed light changes . Our calculations predict the occurrence of g-mode pulsations at the observed variability frequency . On the other hand , the strictly mono-periodic nature of the variability strongly suggests a rotational origin . While we prefer the rotational explanation , the present data leave some uncertainty .