The crowds are thin these days at Detroit Lions training camp. Large sections of empty bleachers are easy to spot.

In most years, the scene on the backfields of the team’s headquarters in Allen Park is festive, even full of possibility. At least you tell yourself that as you watch practice.

This year, the scene is relatively subdued.

Oh, it should pick up next week when the New England Patriots come to scrimmage. And the weekends will free up more diehards.

Still, the lack of fans has been noticeable.

The question is: where are they?

It’s hot, of course. But then it’s usually hot in late July. Parking isn’t as easy as it used to be, either; fans get bused in from a nearby mall.

And if you’re trying to be generous, you could argue that the deluge of rain in June postponed outdoor trips would-be fans are taking now.

The more plausible explanation for the downturn in attendance is buy-in. A growing number of fans don’t have it.

It’s hard to blame them.

Folks will endure all manner of inconvenience to get next to a winner. Or even an endearing loser. The Lions are neither.

They are stuck in purgatory. Victories this fall could change this. So could signs of progress — tight losses to good teams after good play.

But it’s hard to forget the end of last season. It’s also hard to forget the last half-century.

So maybe fans are staying home until they see some proof. A road win against a good team, perhaps. Evidence of a running game. A bounce-back month from quarterback Matthew Stafford.

Last year’s narrative fell apart in a flash. The Monday night opener against the Jets was a debacle. Somehow, the finish felt worse — the Lions lost four of their last six games, including a dispiriting setback against Buffalo.

Training camp usually washes away the sins of the previous season. It’s been that way here for decades. Credit the unending faith of the faithful. The same romantic souls who file into Ford Field every September hoping this finally will be the year their love is returned.

Well, maybe they’ve had it.

Maybe they’ve withheld their unconditional support until head coach Matt Patricia and general manager Bob Quinn give them a reason to show support.

Maybe this is a reckoning. And the first signs of it have shown up in the form of empty bleachers. Bleachers, by the way, that cost nothing in which to sit.

This is partly why the scene at Lions headquarters Tuesday was so jarring. Outsized training camp crowds had become a franchise tradition.

Just like in-their-prime Hall of Famers walking away.

It’s possible that the larger sport-loving public here is fighting off a malaise this summer. None of the four professional teams are close to being a contender in their sport.

Unless it’s the Lions.

That’s always been the thinking, anyway. Particularly this time of year.

Fans here understand the NFL is set up for its worst teams to get better in a hurry. They know the Rams — the Rams! — played in the Super Bowl seven months ago.

That undercurrent of optimism is an important part of why so many return every fall no matter how miserable their team performed. It’s a sentiment on which the Lions rely.

Yet for the first time in memory, that sense of eternal hope has gone missing for most of the first week of training camp. It’s been kind of quiet in Allen Park, frankly.

Oh, there are fans. And families. And kids wearing Stafford jerseys.

Just not as many of them.

So call it a message. Maybe not planned. Maybe made worse by the vagaries of summer vacations and inconvenient bus rides. But a message nonetheless.

It's time to win. Do that and they will come to see more than just Tom Brady next week.