In a note to clients — as noted by “Fortune” William Blair’s Anil Doradla notes that although Apple’s iPhone is still America’s bestselling high-end smartphone, its sales momentum is “under pressure,” particularly at Verizon.

According to Doradla’s channel checks for the June quarter, the iPhone is no longer the top selling smartphone at Verizon’s retail outlets. The analyst attributes the iPhone’s fall from grace less to the usual slowdown in advance of a new model than to Verizon’s aggressive marketing of competing 4G devices, particularly Motorola’s Droid RAZR MAXX, notes “Fortune.”

On the other hand, “AppleInsider” notes that Canaccord Geunity analyst Michael Walkley says the iPhone IS still the top-selling smartphone for Verizon. aid while the latest Razr is “gaining ground,” it “hasn’t caught iPhone.” His own research has found the iPhone 4S as the top selling smartphone at Verizon, as well as AT&T and Sprint, for all of 2012 so far.

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