Jaroslaw Niezgoda scored twice during a six-minute stretch early in the second half, and the streaking Portland Timbers defeated the visiting San Jose Earthquakes 3-0 on Sunday evening at Providence Park.
The goals were the fourth and fifth of the season for Niezgoda, and marked his first multi-goal game in MLS since signing with Portland from Legia Warsaw in his native Poland prior to the season.
Felipe Mora added his seventh goal of the season for the Timbers, who won their fifth match in a row to move level on points with the Seattle Sounders atop the Western Conference standings.
The Sounders currently would edge the Timbers on the first tiebreaker with a goal difference of plus-18, nine better than the Timbers' plus-9.
Tanner Beason had a second-half goal disallowed for San Jose, which had its own winning streak snapped at three games.
Niezgoda put Portland ahead only seconds into the second half, reaching Chara's cross from the right flank and sending a looping header back across Marcinkowski's body and across the goal line.
Marcinkowski could do little to stop that opening tally, but the same could not be said six minutes later, when he came off his line to snuff out Diego Valeri's breakaway opportunity but failed to control the ball.
Beason then compounded issues with a poor clearance attempt that fell straight to Niezgoda, who from just above the penalty arc finished low and true into an open goal.
That was more than enough for Clark, who made an excellent point-blank stop of Chris Wondolowski in just the sixth minute, and also reacted well to turn away Tommy Thompson's header at the far post in the 60th minute.
Mora added his goal off Chara's second assist in the 86th minute.