Wearing a natty, dark suit, white shirt and striped tie, Clooney posed for photos and signed autographs while strolling across cobbled streets in the historic part of the city.
The actor was invited by Americans Abroad for Obama to attend a fund-raising reception, followed by a dinner at the home of Charles Adams Jr, an American lawyer based in Geneva.
Wealthy supporters paid $5,000 to pose for a photo with Clooney, while around 100 guests attending the reception forked out $1,000 each.
A small group of 35 people coughed up $15,000 per person (less than initially advertised) to break bread with the movie star at the catered dinner at Adams’ home with its view overlooking Lake Geneva.
Clooney “spoke for about three to four minutes, very little”, Walter Furth, a former chairman of Democrats Abroad Switzerland, told Reuters Television after the reception.
“He just said we're doing good work and to keep it up."
The fundraisers were similar to events in Geneva that Clooney participated in four years ago for Obama’s successful election campaign, reportedly raising more than $900,000.
The actor travelled to Geneva from his villa near Lake Como in northern Italy, where he often spends time in the summer.
Newspaper Le Matin reported earlier that Clooney had wanted to ride his Harley-Davidson motorbike to the Swiss city but organizers convinced him to take a safer journey in a chauffeur-driven limousine.
The actor is a longtime supporter of Obama, who is dueling for re-election in November against Republican Party candidate Mitt Romney.
Both candidates are engaged in mammoth fund-raising efforts. There is no word yet on whether the campaign team for Romney, who reportedly has a Swiss bank account, is planning any events in Switzerland.
Clooney recently used his star power to raise $15 million for Obama at a dinner held in his Hollywood mansion.
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