Sir Alex Ferguson's side currently lead local rivals Manchester City by 15 points, and the former Liverpool manager thinks that Van Persie's decision to join United over City has been crucial to the Red Devils' cause.
"The defining moment of this season's title race happened before a ball had even been kicked – when Robin van Persie chose Manchester United over neighbours City," Dalglish wrote in his column in The Mirror.
"He may not have scored many recently, but so many of Van Persie's goals earlier in the season have gone a long way to establishing United's 15-point lead over their rivals.
"It's the significant goals, those that win tight games, that matter, and Van Persie has done that on several occasions this season. That's been the difference between the clubs."
The Dutchman signed for the club from Arsenal for a reported £25m last summer.