The majority owner and former COO replaces Chris Raih, who will serve as president going forward.
Julie Fleischer, who will be vp of product marketing, brings 20 years of marketing industry experience to the real-time data provider, where she will handle strategy, messaging and execution.
The British copywriter and art director also worked on such thoroughly U.K. brands as Harvey Nichols, Halifax and ... Google?
Mercer, who just joined the New York team in May 2016, was key in helping the agency win social and digital work for Busch.
Saatchi & Saatchi Los Angeles veteran replaces Harvey Marco, who left the dedicated shop last fall after 6 years.
Jay Kamath and Matt Johnson launched the creative agency in Los Angeles at the beginning of February.