The pitch, which also included Abbott Mead Vickers BBDO, was sparked by a shift of the US business from McCann to DDB Chicago at the end of last year.
McCann-Erickson originally won the combined account following a review triggered by the closure of incumbent D'Arcy after its purchase by Publicis in 2003.
Capital One's planning and buying, which is handled by Starcom Mediavest, was unaffected by the pitch.
Last month, Capital One became the UK's first credit card company to use the fear of identity theft to market its products, running a two-month, £4m TV campaign starring TV impressionist Alistair McGowan.
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