Because the atmosphere is so thick on Venus, however, it's like as if Earth had no continents with a swift equatorial ocean current. So, I can see how the effect on Venus' rotation would be significant. Once the air currents got rolling, they would take on a life of their own (just like bathtubs that drain in a clockwise direction in the north.) So, the current winds on Venus are essentially a living fossil--evidence of a more primitive, prograde existence. (Check out papers written by Cheng Zhi Zhang in the Harvard database.) Zhang argues that the atmospheric tides are strong enough to counterbalance the tidal torque exerted by the Sun, and thus make possible the tidal Earth/Venus resonance that makes Venus always present the same side to Earth during Earth/Venus/Sun conjunctions.