Theories on blocking vary from Stewart's 'never' to those who do it to hang on for a win

Theories on blocking and when it is acceptable vary widely in the NASCAR garage.

Tony Stewart insists it's never acceptable, and others like Joey Logano and five-time series champion Jimmie Johnson feel that all bets are off when trying to protect a victory late in a race.

The next chance for the drivers in the Sprint Cup Series to demonstrate their thinking comes Sunday at Martinsville Speedway, where it's almost impossible not to get in someone's way, and often good strategy.

Stewart says his position blocking has never changed, but the tactic is growing in popularity.

Johnson says it's important for drivers to know that if they block a competitor from getting past them, or take their preferred racing line away, there may be consequences.