One day, it is going to end. Jimmie Johnson knows this. One day someone else will be the dominant driver on the Sprint Cup circuit, and Johnson will be chasing him, just as everyone is currently chasing Johnson. Although it seems difficult to believe now, as the Hendrick Motorsports driver and his invincible No. 48 team charge toward their fourth consecutive championship, the cyclical nature of NASCAR will at some point inevitably topple them from the summit.

There's a reason why, over nearly six decades of competition, only one man was able to win three straight championships. There's a reason why, before Johnson, nobody seriously threatened to win four in a row.

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When that day comes, I hope I can handle it as well as the guys I've respected growing up have, because it won't be easy. Losing sucks. We all hate it.

”

JIMMIE JOHNSON

They say the only constant in NASCAR is change, and over time change will wear anyone down -- even Johnson, although right now he looks like he could go on winning titles forever. At some point, he'll take a step backward, begin to decline. He knows this as well as anyone else. Mentally, he's even begun to prepare for it.

"I'm well aware that things have gone great for the last three years. I'm obviously hoping for a fourth," he said. "But at some point I won't be that guy. It will be somebody else. Somebody else will be doing it. I've always been aware of those things through my career. I've been very fortunate to race with and be mentored by other champions and guys that have been very successful. To watch how graceful they've been, [motocross legend] Rick Johnson, [ASA champion] Gary St. Amant, Jeff Gordon, there have been a lot of guys through the years that have worked with me. I've been aware of that, and I've always in the back of my mind said, 'That's how I want to kind of handle things, to be and act.' I do pay attention to that. I am aware of it. When that day comes, I hope I can handle it as well as the guys I've respected growing up have, because it won't be easy. Losing sucks. We all hate it."

And yet, it may be a while still before Johnson has to deal with it. A 25th-place finish Sunday at Homestead-Miami Speedway will net him an expected fourth straight crown, and he'll undoubtedly be the favorite to win his fifth next season. Johnson is in the midst of a historic, unprecedented stretch of success, one which defies all the usual NASCAR caveats about how difficult it is to stay on top. Today, Johnson and his team look every bit as flawless and as bulletproof as they did in 2006, an eternity ago by the standards of this sport. It could be years and years still before they come back to the field. And by then, this former unknown from El Cajon, Calif., could be well on his way to becoming the greatest NASCAR driver of all time.

Usurping the holy trinity of Richard Petty, Dale Earnhardt, and Jeff Gordon? Should Johnson take care of business on Sunday, it's absolutely and completely possible. No question, getting there would be fraught with difficulty, and clearly Johnson's smooth, unflappable style makes all this look much easier than it really is. But everything, from his age to the state of the sport today, is on his side. Given what he's already accomplished, and the potential he still has in front of him, there are no limits to what he may achieve.

Take any favoritism or bias out of the equation and look at this from a cold, logical point of view. First, there's Johnson's relative youth. At 34 years old, he'll be the second-youngest driver to reach four titles. Petty was 35 -- not a bad parallel, actually -- and Earnhardt 39. Gordon was 30, and after his fourth title in 2001 heard the same "seven championships" talk that Johnson is hearing now, to the point where even the mention of it still ruffles him a little bit. But eight years ago, the sport was completely different. The championship was determined over a full season, the car was so pliable that crew chiefs could make huge strides in a relatively short time, there were a dozen teams capable of winning races, and it was much, much harder to stay on top than it is today.

Johnson has the benefit of timing. His rise coincided perfectly with the implementation of the Chase, which not only resets the points after 26 races -- although this year we'd have a closer race under the old system, with Johnson leading Tony Stewart by 13 -- but also features a 10-race playoff dominated by some of Johnson's best tracks. As it stands now, a Chase with Dover, Charlotte, California, Martinsville and Phoenix allows Johnson to bring a howitzer to a knife fight. He'll continue to enjoy that advantage unless NASCAR makes changes to the latter third of the Sprint Cup schedule, something that won't occur until 2011 at the earliest, if it happens at all.

Team chemistry

Drivers don't win on their own and crew chief Chad Knaus -- whose proficiency with the current vehicle speaks for itself -- is to share the credit for Johnson's success.

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Then there's the vehicle itself. By design, the current Sprint Cup car is encapsulated in a much more rigid technological box than its predecessor, a fact that not only makes it harder to cheat, but also may be slowing the sport's cyclical nature, and theoretically make it easier to stay on top. With the old car, there was a clear pattern: one team would hit on something and nose out front, then everyone would catch up, then another organization would take the lead. It wouldn't be uncommon for four or five teams -- say a DEI, a Hendrick, a Gibbs, a Robert Yates Racing, an RCR, a Penske, even a Bill Davis Racing -- to enjoy periods of prolonged success within a span of a few years.

Now, the limitations of the current car appear to be making it more difficult for everyone else to catch the leaders, which in this case are Hendrick and the No. 48 team. After some initial stumbles, crew chief Chad Knaus found a firm handle on the new car, and hasn't let it go. Would things be different with the old vehicle?

"It may have been a little bit easier to get an advantage in the old car, so with that being the case, I could make a case for yes, it could potentially be a little bit easier to run somebody down in the old car," said Alan Gustafson, crew chief for Mark Martin, currently 108 points behind Johnson. "I don't think it makes a ton of difference. This car does have a little tighter box to where it's tougher to get an advantage. Obviously Chad and Jimmie have a great relationship and they're a great team and they really work well together, and that makes it tough. To beat them, you have to have some advantage over them. Maybe the old car would give us a better opportunity to do that, but if so it would be very slight."

But in a sport where tenths of a second make a huge difference, a slight advantage can go a long way. The teams chasing Johnson don't have that advantage anymore. And many of them don't have enough sponsorship money, either, given the effect the recession has had on the companies that back NASCAR entries. Heading to Homestead, nine teams have won Sprint Cup races this year, a number that includes Michael Waltrip Racing's victory in the rain-shortened Coca-Cola 600 and Phoenix Racing's victory at Talladega. Again, let's look back to Gordon's last championship season of 2001, when a dozen outfits found their way to Victory Lane, smaller programs like Wood Brothers, Andy Petree Racing, Bill Davis Racing, and PPI Motorsports among them.

Those days are gone. The sponsorship shortage has completely gutted NASCAR's middle class, forcing a number of programs to be shuttered, merged, or contracted. The pool of organizations legitimately capable of winning races is shallower than it was eight years ago. How does this affect Johnson? Simple -- there are fewer teams out there that have a hope of beating him. A decade ago, Bill Davis and Robert Yates fielded cars that were championship contenders. Five years ago, DEI had three cars that could win races, and Evernham Motorsports had two. Now even RCR, as storied a program as there is in NASCAR, struggles to stay on its feet. The car is tougher to get a handle on, sponsorship money is tougher to come by, and it's that much tougher to catch Johnson as a result.

Of course, much of Johnson's success is due to Knaus, whose proficiency with the current vehicle speaks for itself. They've been together since Johnson moved into the Cup circuit full-time in 2002, and other than a fractious 2005 season that nearby broke them up, have worked together seamlessly. Eight years is a long time for a crew chief and a driver to be together, but Johnson and Knaus show no signs of breaking up. Ray Evernham won three titles with Gordon, and then left to go into team ownership. Knaus once hoped to do the same thing. But the economics of today's NASCAR make that a substantially larger undertaking than it was in 2000, when Evernham went out on his own.

"My initial goals when I first came into the Cup Series were to obviously become a crew chief and win races and win a championship, and then move on to an ownership role. I don't know if I want that now or not," Knaus said. "I think it would be foolish of me to try and think I could be an upstart team and make something like that happen. You almost have to have an affiliation with somebody to do that. I think you look at Tony Stewart and the way he got into Stewart-Haas and how that deal all came together with support from Hendrick Motorsports, that deal will work. To start an outside company would be a pretty lofty goal, and after realizing what we have here at Hendrick Motorsports, I don't know if I ever would want to race against it. It's a pretty amazing place. So I don't know. We'll have to wait and see. But the likelihood is probably slim at this point."

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Again, Johnson benefits from timing. These days, it just isn't feasible for Knaus to try and follow the Evernham model. The result is that he and Johnson stay together longer, and the strength of that relationship is clearly evident on the race track. NASCAR hasn't seen a crew chief and a driver maintain a relationship this long and successful since the days of Petty and Dale Inman -- and we all know what they achieved together.

No question, there will be obstacles. Eventually, the Gibbs and Roush camps will begin to turn out more consistent race cars, and drivers like Kyle Busch and Carl Edwards will benefit as a result. But Johnson's greatest hurdles may come from within. There's his own organization, for one, which this year produced three legitimate championship contenders -- four, if you include Stewart's affiliated program -- and indeed it appears that the greatest threat to Johnson's dominance may come from within his own shop. There may well come a time in the near future when crewmen on the No. 48 squad are called upon to help rescue a damaged, points-leading car driven by Martin or Gordon, just as mechanics from those teams did after Johnson crashed at Texas two weeks ago.

But the one thing most capable of preventing Johnson from becoming the greatest driver of all time may be Johnson himself. This is a different era of different drivers, men who understandably would rather enjoy the fruits of their labor than wrestle a steering wheel until they're 50. By his own admission, Johnson likes his free time, likes to travel, likes to spend time with his family and his wife. He isn't the type of guy who's going to spend an off weekend driving a sprint car on a dirt track. He rarely competes in the Nationwide Series, doesn't own even a low-level racing team. His competitive edge is always there, simmering beneath his sunglasses, constantly on a slow burn. But if one day he walked away, content and fulfilled and happy, would anyone be surprised?

Not a bit. Granted, there are no signs of that happening anytime soon. But Jimmie Johnson isn't the kind of driver who'll feel compelled to stay in the race car any longer than he wants to. He surely won't need the money, and he damn sure won't become one of those past-their-prime drivers always working the garage looking for another ride. Does he have the chance to become the greatest of all time? Absolutely. Whether he wants to, though, is a question only he can answer.

The opinions expressed are solely those of the writer.