Nationals 7, Cubs 2: Adam LaRoche homered and drove in two runs as visiting Washington completed a doubleheader sweep to salvage a split of the four-game series.Wilson Ramos added a solo blast, Kevin Frandsen went 2-for-3 with an RBI single and Nate McLouth had two hits and scored twice to move the Nationals into a tie with Atlanta for first place in the National League East. Blake Treinen (1-3) survived a 55-minute rain delay to earn his first major-league victory, allowing two runs on four hits over five innings, and Ross Detwiler tossed three scoreless frames for his first save.Luis Valbuena belted a two-run homer for Chicago, which tumbled to its sixth loss in nine games. Jeff Samardzija (2-7) was tagged for six runs - five earned - on seven hits in five innings to extend his winless drought to four starts.LaRoche led off the second with a homer to right and Anthony Rendon, who had three hits in the opener Saturday, doubled the lead with a sacrifice fly in the third inning. Valbuena knotted it in the fourth, following Starlin Castro's single with a blast to right just before the rains came, forcing the 55-minute delay.Samardzija came out for the fifth and was greeted by Wilson's leadoff homer before Washington tacked on three more runs with two outs in the inning. After McLouth was hit by a pitch and Rendon singled, Frandsen and Werth delivered back-to-back RBI singles to make it 5-2 before first baseman Anthony Rizzo's error plated another run.GAME NOTEBOOK: Rendon went 7-for-16 with three RBIs in the series. ... Nationals LF Bryce Harper, who has been sidelined since tearing a ligament in his left thumb on April 25, hit three homers in a rehab game for Double-A Harrisburg and is expected to join Washington for Monday's home game versus Colorado. ... Chicago, which has scored two runs or fewer in 11 of Samardzija's 17 starts, will have its first scheduled Sunday off in 82 years because of the city's Pride Parade before kicking off an 11-game road trip Monday in Boston.