The Washington Post's Cindy Boren describes the fatal accident Saturday night at a dirt-track race in Canandaigua, N.Y., where Tony Stewart's car struck and killed fellow driver Kevin Ward Jr. The popular NASCAR driver, who was a regular on the dirt-track circuit, now faces an uncertain racing future. (Jhaan Elker and Kate M. Tobey/The Washington Post)

In the blink of an eye, everything changed for one of the most popular and successful drivers in NASCAR.

Tony Stewart was behind the wheel of a dirt-track race car that ran over and killed Kevin Ward Jr. in a race Saturday night and his future has been plunged into uncertainty. There are key NASCAR Sprint Cup races coming up, but will the three-time Sprint Cup champion drive in them? Could the ongoing investigation result in criminal charges, even though none are pending now? What is Stewart’s role, as owner and driver? Are sponsors likely to abandon him? Will there be long-range implications for him?

After a member of his team said hours after the crash that Sunday’s race at Watkins Glen would be “business as usual,” it quickly became apparent that it would be anything but that. Video of the incident prompted a visceral reaction, one that led Stewart to reconsider. After conferring with Greg Zipadelli and other members of Stewart-Haas racing, he alone, according to Zipadelli, reached the conclusion that Regan Smith should drive his No. 14 car. But we haven’t heard that from Stewart himself yet. He was described by the sheriff in Ontario County, N.Y., where the incident took place, as “visibly shaken” afterward and, on Sunday, he said in a statement:

“There aren’t words to describe the sadness I feel about the accident that took the life of Kevin Ward Jr. It’s a very emotional time for all involved, and it is the reason I’ve decided not to participate in today’s race at Watkins Glen. My thoughts and prayers are with his family, friends and everyone affected by this tragedy.”

On Friday, Tony Stewart practiced for Sunday’s Watkins Glen race. (Derik Hamilton / AP)

The most immediate question involves his status for Sunday’s Pure Michigan 400. Stewart presently is 21st in Sprint Cup standings and needs to race for the points, but it’s anybody’s guess whether he will do so. “The decision to compete in this weekend’s NASCAR Sprint Cup Series event at Michigan will be Tony’s, and he will have as much time as he needs to make that decision,” Mike Arning, the director of Stewart-Haas Racing, told USA Today. “It is still an emotional time for all involved, Tony included. He is grieving, and grief doesn’t have a timetable.”

However, he will not drive in the Plymouth, Ind., dirt-track race on the eve of the Michigan race, the Plymouth racetrack announced Monday.

At the moment, there are no criminal charges pending against him as the investigation continues, according to Sheriff Philip Povero. Investigators are still sorting through videos and still photos (while asking for anyone with more to come forward), awaiting autopsy results and speaking with racing experts about the safety of the track and lighting. They spoke to Stewart after the incident in Canandaigua and again Sunday at Watkins Glen.

“We have consulted with the district attorney,” Povero told CNN on Monday morning. “and although … there are no criminal charges pending at this time, this is an ongoing investigation and all options remain available, or open, at this time.”

Stewart is also in a unique position as an owner/driver. The Stewart-Haas team met with him after the accident and into Sunday morning. At some point, he may well have to step back to determine whether this is having an effect on his business, separate from his racing career.

And sponsors could exert an influence there. One of NASCAR’s most marketable drivers, there has been no reaction so far from Coca-Cola, Chevrolet, Mobil 1, Bass Pro Shops or Rush Truck Centers. Past eruptions of his famous temper haven’t cost him any sponsorships, but this is fresh territory. Stewart has, in the past, undergone anger-management counseling and has been placed on probation by NASCAR.

For Stewart, who has long risked his personal health to indulge his passion to revisit his racing origins on dirt tracks, the certainties that racing provides him are suddenly gone.