O'Kelly Variation, Maróczy Bind, Paulsen Line

With 3...e6 Black adds the e-pawn to the a6 and c5 pawns. This gives the familiar Kan formation, and the line's name recalls the Kan's other name, the Paulsen Variation. The move opens the f8-bishop's diagonal and keeps ...d5 available as a way to strike at the c4–e4 pair. Because White has not yet played d4, Black also keeps the choice of when, or whether, to exchange on d4. Wikibooks describes 3...e6 as the most common reply at master level.

The usual answer is 4. Nc3, played in about half the games. It adds control of d5 and keeps d4 in reserve. 4. d4 opens the center at once and can transpose to a Kan in which c4 is already on the board. The quieter 4. d3 keeps the structure closed and is less frequent. The engine gives White a slight edge and prefers 4. Nc3, 4. Be2 or 4. a3. In online play the results are nearly even, with Black scoring marginally better.