The Col de Pailheres came first — a ferociously tough ascent for about nine miles at a gradient of eight percent — and then a shorter but even steeper ride to the finish at the ski resort of Ax 3 Domaines.
Colombian rider Nairo Quintana broke away to launch a brutal attack up Pailheres, and only Frenchman Pierre Roland initially followed him, but Porte helped Froome steadily gain ground on them.
Schleck, Evans and then Rolland were dropped with about 6 kilometers (4 miles) left to go up to Ax 3 Domaines as Contador desperately tried to stay on Porte's wheel.
Porte had tired Contador to the point that the Spaniard was even struggling to keep up with teammate Roman Kreuziger, so Froome decided it was time to finish him off.
"I am little bit surprised," Froome said. "Maybe he (Contador) didn't have his best day today."
Froome climbed with such blistering acceleration it almost looked like he was riding a time trial, blowing past Quintana and then Porte.
"It may look easy on TV but it wasn't," Froome said.
Still, he had time to ease up in the saddle, raise his arms and soak up victory in the blazing sun.
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