Basle coasted to a 3-1 victory at home to Europa League Group E strugglers CSKA Sofia to go two points clear at the top of the table.
The Swiss began the game with a one-point advantage over Fulham - but after the Cottagers' defeat at Roma, the Italians are Basle's nearest challengers.
A goal in each half from Alexander Frei and one before the break from Marcos Gelabert did the trick for the hosts, who soon regained control after Todor Yanchev got one back for CSKA early in the second half.
After a cagey opening, the first shot in anger was CSKA defender Hugo Baez's eighth-minute effort - which cleared the bar from distance.
Marcos Marquinhos' free-kick shortly afterwards merely gave Basle goalkeeper Massimo Colomba some routine catching practice. But it was Basle on the back foot - and regular free-kicks were being conceded.
The hosts roused themselves in the 24th minute when Samuel Inkoom's cross found striker Frei for a right-footed shot from the edge of the box, which flashed wide.
Marquinho shot over from 25 yards shortly before the half-hour, by which time CSKA had made an enforced change in the midfield - Nikolay Manchev coming on for the injured Viktors Morozs.
It was still against the run of play, though, when Basle took the lead - via a 25-yard right-foot shot from Gelabert 10 minutes before the break.
Before CSKA had time to recover their composure, it was 2-0.
Aleksandar Branekov conceded a penalty with a foul on Frei, who got to his feet to convert the chance powerfully into the bottom left-hand corner from the spot.
CSKA hinted at a revival, first when Ivan Stoyanov shot from just outside the area - cleared by Cagdas Atan - and then when Marqinhos' header brought a save from Colomba.
Basle failed to heed the warnings, though and found their lead cut just before the hour when Yanchev got on the end of a Marquinhos corner with a right-foot finish which was too hot for Colomba.
But the fightback did not last long, Frei restoring Basle's two-goal cushion and completing the scoring in the 67th minute when he latched onto a good pass from Benjamin Huggel and beat Zdravko Chavdarov with his left foot from outside the area.
