Lausanne - American Larry Warbasse won Tuesday's Tour of Switzerland fourth stage at Villars-sur-Ollon as Italy's Damiano Caruso pulled on the leader's yellow jersey.
Warbasse, 26, was the lone survivor from a 150km breakaway in the mountain stage, and reached the summit finish 40 seconds ahead of Caruso, who took the overall race lead from Australian sprinter Michael Matthews.
The yellow jersey has now changed hands four times in four days, with BMC rider Caruso 15 seconds clear of Dutchman Steven Kruijswijk.
It was the first win of his career for Aquablue rider Warbasse, a former member of the now-defunct Swiss team IAM Cycling, after he found himself a minute clear of his fellow escapees with only 2.3km remaining.
"I love this race, l love Switzerland, I was on IAM for two years," an emotional Warbasse said.
"It felt like a home race today. Everybody was yelling my name and I'm so happy."
AG2R La Mondiale's Domenico Pozzovivo finished four seconds behind Caruso and Kruijswijk on the day to move third in the overall standings.
Wednesday's 222km fifth stage from Bex to Cevio is the longest of the nine-day Tour of Switzerland, which is one of two main pre-Tour de France warm-up events, despite losing prestige compared to the Criterium du Dauphine in recent years.
While the winner of the Dauphine went on to win the Tour in four out of five years from 2012 to 2016, the last time a Swiss Tour champion also claimed Grand Boucle glory was Belgian great Eddy Merckx in 1974 - although disgraced American Lance Armstrong did that particular double in 2001 before being stripped of both results for doping.
Results from the 150.2km fourth stage of the Tour of Switzerland from Bern to Villars-sur-Ollon on Tuesday:
1. Larry Warbasse (USA/ABS) 3hr 48min 55sec, 2. Damiano Caruso (ITA/BMC) at 0:40, 3. Steven Kruijswijk (NED/LNL) 0:40, 4. Simon Spilak (SLO/KAT) 0:40, 5. Domenico Pozzovivo (ITA/ALM) 0:44, 6. Mathias Frank (SWI/ALM) 0:47, 7. Marc Soler (ESP/MOV) 0:59, 8. Miguel Ángel López (COL/AST) 1:07, 9. Mikel Nieve (ESP/SKY) 1:20, 10. Rui Costa (POR/EAU) 1:34
1. Damiano Caruso (ITA/BMC) 12hr 08min 35sec, 2. Steven Kruijswijk (NED/LNL) at 0:15, 3. Domenico Pozzovivo (ITA/ALM) 0:24, 4. Simon Spilak (SLO/KAT) 0:24, 5. Marc Soler (ESP/MOV) 0:31, 6. Mathias Frank (SWI/ALM) 0:33, 7. Mikel Nieve (ESP/SKY) 1:09, 8. Rui Costa (POR/EAU) 1:10, 9. Valerio Conti (ITA/EAU) 1:20, 10. Miguel Ángel López (COL/AST) 1:25.