After the Chicago race (where #17-Matt Kenseth was penalized for being pushed on the final lap after he ran out of fuel), NASCAR told teams that they'd be watching this issue of assisting another car more often the rest of the season. So, already, NASCAR is on the lookout for this more often.
Then came the Harvick situation today. At first, he slowed way down and fell off the rear bumper of the car in front under caution _ NASCAR's rule book requires drivers to "maintain a reasonable speed'' under caution. So, NASCAR officials wanted Harvick to maintain reasonable speed and to close the gap with the car in front under caution (NASCAR likes the field tight to limit how much of the track cars are taking, making it easier to move emergency equipment and clean-up vehicles, if needed, around the track).
With NASCAR already putting word out that it was going to look more closely at cars assisting others, series officials reacted. What I was told was that NASCAR doesn't like this because of the advantage it can provide. Also, this is something not all teams can equally do since not all cars have teammates and thus could be at a disadvantage to a multi-car team. In a way, Harvick can say there's no rule that prohibits it. NASCAR can also say that it adjusts things as it goes and this is one of them. What would seem to be the best situation is for NASCAR to write a rule that either prohibits a car pushing another or provide further guidelines on when it is acceptable and when it is not. Don't be surprised if there's a new rule on this in next year's rule book. Virginian Pilot