BETHEL — With one long night of racing remaining, defending Kuskokwim 300 champion Pete Kaiser of Bethel left Kalskag at 7:50 p.m. Saturday, the leader of the world's richest middle-distance race heading into the last 95 miles of icy trail.

After not seeing a Yukon-Kuskokwim-based musher win one of Alaska's biggest races for 29 years, Bethel fans could end up cheering back-to-back titles for a hometown hero, while Kaiser could claim $25,000 of a record $130,000 purse with a win.

Kaiser's lead was slim. Joar Ulsom of Norway pulled out 19 minutes later, and 2015 Yukon Quest champion Brent Sass of Eureka left 13 minutes after Ulsom.

The last part of the race can be rugged and confusing — even dangerous. As recently as last year, mushers have taken wrong turns that cost them gobs of time.

"It's an ice trail," race manager Zach Fansler said. "It's got grip in places but ice trails are hard, and hard on equipment."

Earlier Saturday, Kaiser spotted an unmarked open hole that appeared to have just developed on the Kuskokwim River about 12 miles from Aniak between that village and Kalskag, Fansler said. It's near another well-marked open hole. Kaiser reported it and trail crews rushed to mark it, Fansler said.

Crews also will be out to make sure mushers see it in the dark, since it appears to have opened up after they passed that way heading upriver and before their return trip to Bethel.

Sass was driving 10 dogs but was without the lead dog that led him to his Quest win last February — 5-year-old Basin died earlier this week on a training run, according to Alaska Public Media.

"I left the dogs camping like I always do and when we came back down to the dogs, something had definitely happened," Sass told APRN. "He'd gotten sick and was not in a good way. It went downhill fast."

Because Sass and his team were in a remote area, the musher couldn't summon a veterinarian. "We did as much as we could," he said. "We gave him fluids and warmed him up and put him in a cabin. But we couldn't (save him)."

The victor is expected to cross the finish line Sunday morning.

Reporter Lisa Demer in Bethel contributed to this report. Contact Mike Campbell at mcampbell(at)alaskadispatch.com.