The Double-A Harrisburg Senators edged Portland 2-1 to clinch at least a tie atop their division over Richmond. Bowie lost Wednesday so they are eliminated from contention for the division title.
The Senators (78-59) have five straight games remaining at home. Any combination of one Senators win and a loss by Richmond (73-64) and Harrisburg clinches the top spot in the division.
Right-hander Stephen Strasburg can clinch the division and will pitch his final minor league rehab assignment Thursday night.
He is scheduled to go five innings and a maximum of 80 pitches. Strasburg is expected to be activated for Tuesday's Nationals game at home against the Los Angeles Dodgers.
The Senators Tim Pahuta smacked a fifth inning solo shot and Tyler Moore delivered the eventual game winning two-out RBI single in the eighth to lift Harrisburg to the 2-1 lead.
Erik Arnesen allowed one unearned run over seven innings. Cory Van Allen (5-3) pitched the eighth for the win and Rafael Martin notched his 13th save with a scoreless ninth.