Over the decades, Bill Murray has evolved into a kind of national institution of pop culture. He's the leading natural source of Bill Murray-ness. He is, in his own way, already a saint.

Over the decades, Bill Murray has evolved into a kind of national institution of pop culture. He’s the leading natural source of Bill Murray-ness. He is, in his own way, already a saint.

His new dramedy “St. Vincent” shamelessly attempts to harness as much of the Bill Murray magic as it can. Results are mixed, but at least it’s got Bill Murray.

Vincent (Murray) is a grumpy old man with a penchant for whiskey and horseracing. Maggie (Melissa McCarthy) is a single mother who moves into Vincent’s Brooklyn neighborhood to start a new life with her 12-year-old son Oliver (Jaeden Lieberher).

When the pressures of working momhood leave Maggie in a bind, she reluctantly leaves Oliver in the care of Vincent — who reluctantly agrees after negotiating his babysitting fee. An unlikely friendship ensues, and a softer side of Vincent emerges.

Writer-director Theodore Melfi makes his feature debut with a great cast for the material. Murray and McCarthy are joined by Naomi Watts, who plays a very pregnant Russian stripper.

“St. Vincent” is saddled by its predictability, though. We’ve seen this mix of salty and sweet before. With the Terry Zwigoff retrospective at the Wex, I found the comparison to the far-superior “Bad Santa” to be unavoidable.

Murray gives us a full blast of Bill Murray — a lengthy online clip of him belting out Bob Dylan’s “Shelter From the Storm” was a pretty genius bit of marketing. He also gets to flex his dramatic muscles, although the plot events that cause him to do so border on melodrama.

I felt McCarthy was better in “Tammy,” but then I was the only critic who really loved that. Young Lieberher is suitably adorable, but Watts can’t pull her character past its absurd premise.

The plot unfolds pretty much exactly as you’d expect, and the grouchy old man gags can only go so far, even when your grouchy old man is Murray.

Melfi won the lottery with this first feature, but it’s way too derivative to be worth a strong recommendation for anyone but Bill Murray fans. The good news? Isn’t everyone a Bill Murray fan?

Photo courtesy of The Weinstein Company