Ireland's Nicolas Roche moved into the race leader's red jersey at the Vuelta a Espana after finishing third on stage eight's summit finish on Alto de Penas Blancas.
The day was won by Czech rider Leopold Konig (NetApp-Endura), who attacked 2km out and then held off a late charge from second-placed Daniel Moreno (Katusha).
Roche followed five seconds behind Konig, but with previous leader Vincenzo Nibali (Astana) suffering a poor day and losing 27 seconds, the Saxo-Tinkoff rider moved to the top of the general classification and now leads second-placed Chris Horner (RadioShack-Leopard) by 17 seconds.
The result continues what has so far been an outstanding Vuelta for Roche, who earlier won stage two, but casts doubt over Nibali's credentials after the Italian cracked in the final 1km and was dropped by all of his rivals for overall victory.
It also marked a breakthrough victory for Konig and his NetApp-Endura team, who are competing in their first Grand Tour after being given a wildcard entry.
Joaquim Rodriguez (Katusha) and Alejandro Valverde (Movistar) joined Nibali in dropping time but limited their losses to 19 seconds, while Team Sky's Colombian pairing of Rigoberto Uran and Sergio Henao also wilted at the death and shipped 23 and 27 seconds respectively.
One of the surprise packages of the day, though, was Italian veteran Ivan Basso (Cannondale), who was part of a late counter-attack and finished on the same time as Roche in fifth.
The final climb was the third of this year's Vuelta's 11 summit finishes and provided a dramatic finale to a 166.6km day that had started in Jerez de la Frontera.
A 14-man breakaway, later reduced to 13, opened up an advantage of over four minutes, but by the time they reached the foot of the category-one ascent 14.5km out, it had fallen to less than a minute and their fate was effectively sealed.
Konig makes his mark
RadioShack-Leopard set the pace on the front of the peloton for the first two-thirds of the climb, but the status quo was finally broken just under 5km out, when Igor Anton (Euskaltel-Euskadi) attacked.
Konig then countered with 2km to go and a second chase quartet including Roche and Basso followed, but Nibali, Rodriguez, Valverde and the Colombians remained in the main group.
Konig caught and passed Anton with 750m remaining and was already too far ahead when Moreno and Roche made belated attempts to overhaul him.
In behind, the big favourites had no answer to the flurry of attacks further up the road and instead turned their focus to limiting the damage.
Stage eight result
1 Leopold Konig (Cze) NetApp-Endura, 4:09:46
2 Daniel Moreno (Spa) Katusha, +1sec
3 Nicolas Roche (Irl) Saxo-Tinkoff, +5
4 Thibaut Pinot (Fra) FDJ, same time
5 Ivan Basso (Ita) Cannondale, st
6 Bart De Clercq (Bel) Lotto-Belisol, +8
7 Igor Anton (Spa) Euskaltel-Euskadi, +13
8 Alejandro Valverde (Spa) Movistar, +19
9 Joaquim Rodriguez (Spa) Katusha, st
10 Rigoberto Uran (Col) Team Sky, +23
15 Sergio Henao (Col) Team Sky, +27
16 Vincenzo Nibali (Ita) Astana, same time
1 Nicolas Roche (Irl) Saxo-Tinkoff, 31:39:30
2 Chris Horner (USA) RadioShack-Leopard, +17secs
3 Daniel Moreno (Spa) Katusha, same time
4 Vincenzo Nibali (Ita) Astana, +18
5 Leopold Konig (Cze) NetApp-Endura, +29
6 Haimar Zubeldia (Spa) RadioShack-Leopard, +30
7 Alejandro Valverde (Spa) Movistar, +31
8 Rigoberto Uran (Col) Team Sky, +42
9 Rafal Majka (Pol) Saxo-Tinkoff, +52
10 Joaquim Rodriguez (Spa) Katusha, +1:03
- Green (points classification): Daniel Moreno (Katusha)
- Blue polka dot (mountains classification): Nicolas Roche (Ire) Saxo-Tinkoff