Because right now, it’s one of them, without question. Johnson holds a 30-point lead in the standings, but Kenseth has a series-leading three race wins, and it’s the latter category that will be used to seed the Chase when the 10-race title run opens Sept. 15 at Chicagoland Speedway. The strange thing is, they’re going about it in opposite ways — Kenseth has shown the ability to completely dominate races like a certain five-time champion historically has, while Johnson has maintained an almost understated level of consistency that’s downright Kensethian in its quality.

Either way, they’re presenting themselves as major players almost every week, and Sunday at Dover was no exception. Kenseth dominated early, Johnson dominated late, and the fact that both were resigned to watching Tony Stewart celebrate in Victory Lane shows how unpredictable a single NASCAR afternoon can be. But championships are won not over one race, but over a series of them, and no two drivers this season have proven themselves better suited to prevailing over the longer haul.

It says something that Johnson has maintained his position despite perhaps his roughest stretch of the season, with the restart penalty coming on the heels of a spin in the Coca-Cola 600. He also hasn’t won since Martinsville nearly two months ago, though he’s surely had his chances since then. Likewise, Kenseth can point to several that got away — Talladega and Richmond where he led lots of laps, Daytona and Charlotte where he had arguably the best car. Neither driver has been perfect, as this past Sunday surely attests, but their bodies of work to this point still remain strong enough to elevate them above everyone else.

Now that’s not to discount Kyle Busch, who has won two Sprint Cup races and appeared very capable in several more of them, or Kevin Harvick, who has suddenly emerged to win two of the last six premier-series events. But when it comes to potential top Chase seeds, right now this seems a two-man game. Kenseth lags 74 points behind Johnson in the standings only because he’s suffered a pair of engine failures and a penalty. But have no doubt — these two drivers backed by rival home-improvement chains are the best in the sport right now, and anyone else hoping to make a run at No. 1 is going to have to go through one or both to get there.

So should projections become reality, and Johnson and Kenseth indeed emerge at the top of the field when playoff time begins, who has the edge? At the moment, there seems little doubt that among the two, Kenseth appears the most explosive, belying his unflappable nature. He’s a phenomenal qualifier, and he’s led more laps this season than anyone else on the Sprint Cup tour other than Busch. He’s led laps in all but two races this season, led more than 100 laps four times and seemed poised to lead a lot more at Daytona and Dover had his engines not let go.

Ah, yes. The engine. If there’s a weakness here, it’s the old Achilles’ heel at Joe Gibbs Racing — the hardware. Of course, the engines in this case are made by Toyota Racing Development, which has had six blow in competition so far this season. Kenseth seems at ease with crew chief Jason Ratcliff and his new team, and appears completely capable of becoming the first driver to win a title in his first year with a different organization since Darrell Waltrip did it for another Johnson (that would be Junior) in 1981.

But fair or not, the engine will remain a question mark. Two failures in 13 races is a concerning rate, and recent championship bids by teammates Busch and Denny Hamlin that were derailed by mechanical problems — albeit very different ones — remain too fresh in the mind. To put it in perspective: Kenseth has suffered two engine failures this season, while Johnson has suffered three since the spring of 2008. If there’s any area where Five-Time has a decided edge on the competition, it’s in the historical reliability of his equipment.

Which can make all the difference in a 10-race sprint to the title. In all honesty, Johnson may have a rather comfortable points lead (for the moment), but Kenseth has probably enjoyed the more spectacular season, given how quickly he’s jelled with that No. 20 team and the number of races he’s been in the hunt to win. If there’s any driver who seems capable of winning the Chase the way Stewart did it two years ago, by clubbing the competition into submission with one race victory after another, it’s the one in the No. 20 car. It’s easy to imagine a scenario in which Kenseth has five or six wins already, given how close he’s come so often. He starts finishing the job at the right time — watch out.

Of course, we are talking about Johnson, who over his full-time career has been in the championship mix on the season’s final day in every year but one — 2011, when his five-year reign ended in a mathematical elimination at Phoenix. Subduing the guy is about as difficult as boating a tiger shark. Given what we’ve seen from the No. 48 team so far in 2013, that hasn’t changed. More than a potential mechanical failure, it’s Johnson’s amazing staying power that presents the greatest obstacle for any challenger — even a driver like Kenseth, who currently shapes up as his biggest rival for top seed in the Chase.

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