Halladay, the reigning NL Cy Young Award winner, allowed two runs and six hits to win his 10th straight decision against the franchise from Washington and Montreal. Halladay (5-1) has won 13 consecutive starts against the NL East.
John Lannan (2-4) got roughed up, allowing seven hits and six runs in two-plus innings to fall to 0-10 against the Phillies.
It was the first time since 1929 a game featured one starter with a winning streak of nine or more against a team while the other starter had a losing streak of that length against the opponent. Hall of Famers Lefty Grove and Red Ruffing pitched in the previous one.
The NL East-leading Phillies have won 11 of 14 and are tied with Cleveland for the best record in the majors at 21-9.
The Nationals hadn't been swept this season.
Jimmy Rollins got the Phillies started in a six-run third with a leadoff single. Victorino then hit a high drive down the left-field line that appeared headed foul, but it hooked several feet over into fair territory and landed a few rows deep.
Lannan turned after hanging an 0-1 slider and shouted, "Get foul, get foul, get foul!" Things didn't get any better for the lefty.
Placido Polanco singled, Ryan Howard walked and John Mayberry Jr. ripped an RBI double. Ibanez then lined a two-run double down the right-field line to chase Lannan. Brian Broderick came in and allowed an RBI single to Wilson Valdez that made it 6-0.
The Nationals scored twice off Halladay in the fourth. Wilson Ramos hit an RBI single to score Jayson Werth, who led off with a single. Ibanez made a perfect one-hop throw home from left field that beat Werth, but he slid under catcher Dane Sardinha's tag. Ian Desmond's sacrifice fly drove in the second run.
Ibanez connected off Todd Coffey in the fifth, hitting a 431-foot shot into the second deck in right-center to make it 7-2. He finished with three hits and three RBIs and is 8 for 11 since snapping an 0 for 35 slump.
Notes: Phillies GM Ruben Amaro Jr. said C Carlos Ruiz didn't feel good after taking batting practice and could end up on the disabled list. Ruiz hasn't played since April 27 because of lower back tightness. ... Amaro said injured 2B Chase Utley is making progress. Utley could begin playing in extended spring training by the weekend. ... Halladay is 26-5 against the NL East. ... Lannan's ERA rose from 3.78 to 5.09. ... A crowd of 45,316 was the 153rd straight sellout at Citizens Bank Park, including postseason games. ... The Nationals have lost seven straight in Philadelphia and are 3-21 here since Sept. 26, 2008. ... There was a brief delay in the bottom of the fourth because Coffey's nose was bleeding.
