Four players are tied for the lead in the AT&T National after a lively third round at the Congressional Country Club.
Argentina's Andres Romero is level with Americans Bill Haas, Roberto Castro and James Driscoll on seven-under-par, and a further 10 players are within four shots of the lead heading into the final day.
Castro put an appropriate finishing touch upon a wild day in Maryland by finding water on the 18th but then chipping in for par from 80 feet.
That followed birdies at 16 and 17 and gave him a level-par round of 71, which was a fine effort after he bogeyed two, and then made a double-bogey six at the third.
Nine birdies for Haas
Haas, meanwhile, had no less than nine birdies, but three bogeys and a triple-bogey seven at the 11th meant he finished with a round of 68 which featured just five pars.
Romero's round of 70 also veered from one extreme to the other, as he powered three shots clear of the field with four birdies in an outward nine of 32 but then double-bogeyed 11 and bogeyed 12 to blow his advantage.
Driscoll's round was fairly staid in contrast, five birdies helping him to card a 68, his third straight round in the 60s.
American Jason Kokrak is a stroke back in fifth place after a 70, with compatriot Tom Gillis and South Korea's Charlie Wi a further shot adrift in a tie for sixth after sparkling rounds of 66 and 65 respectively.
Belgium's Nicolas Colsaerts could only manage a 73 and is four shots off the pace at three-under, in a tie for 11th.