General Motors is feeling pretty good about Chevrolet these days, and not without reason. Not everything’s rosy, however.

The brand’s sales are up more than 6 percent this year. It has a strong line of crossovers and traditional SUVs. The new Silverado pickup that goes on sale shortly promises better fuel economy and capability. Enthusiasts are revved about its performance line, which includes the upcoming 2014 Corvette, Camaro Z28 and SS sport sedan. The Cruze compact, Sonic subcompact and Spark minicar comprise by far the strongest small-car lineup GM’s biggest brand has ever offered.

Despite that good news, there’s a new problem in an old familiar sore spot: midsize cars.

The Malibu, the midsize sedan that was a beacon of hope in GM’s darkest days, has gone adrift like a Carnival cruise ship.

The last-generation Malibu, which debuted as a 2008 model, was a triumph. It put Chevy back on a lot of shopping lists with its value, looks, fuel economy and comfort. It beat the Toyota Camry and Honda Accord to win North American Car of the Year. The Malibu provided evidence that GM could build great, affordable family cars.

The new 2013 Malibu that went on sale a year ago has fallen flat. It’s a nonfactor in arguably the most competitive passenger car segment. The Ford Fusion and Nissan Altima eclipsed the Malibu with surprising style and fuel economy, respectively. The new Accord restored Honda’s status as a leader.

Malibu sales are 12 percent below last year’s levels, despite what Edmunds.com says are the highest incentives on any midsize sedan. Overall U.S. vehicle sales are up nearly 7 percent. The Fusion is 25 percent ahead of last year’s pace, the Accord, 26 percent. The Altima is down 3.2 percent, proving that Chevrolet isn’t the only one with problems.

The Malibu takes longer to sell than its competitors. Malibus averaged 107 days on the dealership lot in March, Edmunds said. The next-slowest turning midsize sedan is the Volkswagen Passat at 57 days. VW just dropped a shift at the Chattanooga, Tenn., plant that builds the Passat.

"Chevrolet spent a lot of money advertising the 2008 Malibu," said Edmunds senior analyst Michelle Krebs. "They called it ‘the car you can’t ignore.’ They didn’t advertise the new Malibu, and people are ignoring it. The (Toyota) Camry and Accord are the best-selling cars in America. That should be a Chevrolet."

I’m surprised by the Malibu’s struggles. I’ve tested every version of the car, and I think it’s at least as good overall as the Fusion, Accord and Camry, and more than a match for midsize sedans like the Hyundai Sonata, Kia Optima and Volkswagen Passat.

Not enough buyers are convinced of that.

I suspect the problem, in addition to the lack of advertising, is that the 2013 Malibu lacks any single, outstanding characteristic that shoppers simply can’t ignore. The Fusion has drop-dead looks. The Altima boasts a 38-mpg EPA highway rating. The Accord has a nonpareil reputation and resale value.

What is the Malibu’s bragging point?

Chevrolet hopes to recapture the public’s attention with a 2014 Malibu, scheduled to reach showrooms this summer. Expect minor changes to the exterior styling, improved interior materials and some tweaks to rear passenger room. It’s hard to make a first impression with an 18-month-old car, but Honda performed successful surgery on the Civic.

We’ll see if Chevy can get the Malibu shipshape again.