But perhaps less successfully engineered was the timing of the vehicle's launch, since the compact sedan and hatchback are the first vehicles designed around Mazda's aspiration to become more premium. The timing was problematic, some dealers and analysts say, because Mazda is trying to use a car to do a crossover's job: drive sales gains and elevate its image.

In fact, the Mazda3 is among the brand's poorest sales performers in the U.S. this year and is a significant factor in Mazda's 11 percent sales slump so far in 2019. Through August, Mazda3 sales are down 21 percent from a year earlier, and only the Mazda6 midsize sedan has experienced a bigger slump. The Honda Civic, a close rival to the Mazda3, has posted a 1.3 percent sales increase so far this year.

The Mazda3 remains the brand's No. 2 U.S. seller after the CX-5 compact crossover, which is down 2.7 percent in the first eight months of the year. The Mazda3 is also an iconic Mazda vehicle, with more than 6 million sold since its 2003 debut, according to the company. But the new generation's launch in March has generated mixed feelings.