In its Merger Control Guidelines, the French Competition Authority lists the conditions that lead to the conclusion that the relevant market is affected, which include the disappearance of a potential competitor on one of the markets in which the parties are active. In effect, in certain particular cases, a merger may significantly harm competition by the disappearance of only one potential competitor.

Conversely, the existence of potential competition may constitute a countervailing force to the market power of an undertaking. Even if the latter has a high market share, its power may be effectively limited not only by the response of competitors already present on the market but also by the fact that the market is contestable, i.e. that it is relatively easy for new players to enter the relevant market.