Brendon Todd, coming off a victory two weeks ago in Bermuda, shared the lead with fellow American Vaughn Taylor on Sunday when darkness halted the final round of the US PGA Mayakoba Classic.
Taylor and Todd, both on 20-under par with four holes to finish, were among seven top-10 players yet to finish their final round when sunset fell at Playa del Carmen, Mexico.
Mexico's Carlos Ortiz and American Harris English were on 19-under, Ortiz with one hole to play and English with four remaining. American Adam Long was on 18-under with three holes remaining.
Competition will resume at 7:30 a.m. local time (1230 GMT) with 12 players set to complete their 72 holes after heavy rains washed out play Thursday.
To win, it might take matching or breaking the 72-hole tournament record of 22-under par set last year by Matt Kuchar.
Todd seized the lead with a six-under par 65 in Sunday's third round and players went directly into the last round, rushing in a failed bid to complete 36 holes on the final day.
Todd, 34, won his first US PGA crown at the 2014 Byron Nelson Championship then ended a five-year win drought during which he battled the full-swing yips by taking the Bermuda Championship two weeks ago. This is his first start since that triumph.
"I feel great about my game. Happy to have a chance to win this after winning in Bermuda," Todd said. "I'm excited for the opportunity."
"I'm just trying to hang in there best I can," Taylor said. "Didn't feel too great. I'm tied for the lead. I'm pleased."
"The decision I took not to play, I think was the right one. I have a really good chance to win. Winning in front of my family and crowd would be a dream come true."