THE US's gold medal winners suddenly have two very famous new friends: White House foes Barack Obama and Mitt Romney, who are keen to pick up a glimmer of reflected Olympic glory.

Every four years, the five-ring summer Olympic circus unfolds alongside the one-ring brawl of the White House race, in a volatile mix of flag-waving patriotism and rare national unity ripe for political exploitation.

This year, Romney's dancing dressage horse, gymnastic heroines from swing states and the tax woes of gold medallists have stolen the headlines - during Olympics broadcasts peppered with campaign advertisements.

Given the quadrennial synergy of Olympics games and elections, it is not surprising that campaigns scent political opportunity.

But Olympic politics can be treacherous too, and several presidents have been tested by games darkened by global tensions.

This year, Obama has taken to starting campaign events with praise for the latest triumphs of US Olympians in London.

In Virginia on Thursday, he led a bombastic chant of "USA, USA" and has enjoyed his duty of telephoning gold medal winners, such as swimmer Michael Phelps.

Obama is bursting with national pride over US gymnasts: "I do not understand how, on this little balance beam, you're flipping around. I don't get that."

The sports-mad president also gave a shout out to "Flying Squirrel", double gold medal-winning gymnast Gabby Douglas - who just happens to be from Virginia, a swing state that could help Obama to a second White House term in November.

On Saturday, in his weekly address, Obama noted that in the Olympics, a bitterly divided nation could find common ground.

"These games remind us that for all our differences, we're Americans first," he said.

For a president who has faced fringe charges of not being an American at all, wrapping himself in the Stars and Stripes is a no-brainer less than 100 days before election day.

First Lady Michelle Obama also has an eye for a photo-op. She led the US delegation to London opening ceremonies and was pictured hugging superstars on the US basketball "Dream Team".

For Republican Romney, the Olympics should have offered an easy political win. He is renowned for rescuing the Salt Lake Winter Games in 2002, after a corruption scandal, winning a reputation as a turnaround artist. But the Republican stepped on his own lines last week in an interview with NBC, questioning the UK's preparation for 2012, which ignited a political storm. It was not the only Olympic embarrassment for Romney, who is painted by Democrats as an out-of-touch rich man.

Rafalca, a horse owned by Romney's wife, Ann, featured in Olympics dressage, an expensive and refined sport in which a prancing horse executes moves known as "piaffes" - hardly likely to endear the candidate to the man-on-the-street.

Like Obama, Romney is not below a spot of Olympian pandering, this week praising swimmer Missy Franklin as "just a Colorado girl with a big heart". Like Virginia, Colorado is a key state in November's election.

The former Massachusetts governor has also joined a push to repeal an arcane measure that taxes athletes who bring home gold, silver or bronze medals.

Bygone Olympics have offered presidents moments of political opportunity, or peril.

Ronald Reagan opened the 1984 games in Los Angeles, which turned into an outpouring of patriotism after dark decades dominated by the Vietnam War, the Watergate scandal, an Iranian hostage crisis and a recession.

His predecessor Jimmy Carter, however, had experienced bitter Olympic politics, leading a boycott of the Moscow Games in 1980 to protest against the Soviet invasion of Afghanistan.

In 1996, Bill Clinton got a good re-election year photo-op with Muhammad Ali, who lit the flame for the Atlanta Games.

In 2008, George Bush had an Olympian conundrum, as Dem-ocrats called on him to boycott the Beijing opening ceremonies in Beijing to protest human rights abuses. But he went anyway, reasoning that the vital China-US relationship would be damaged by staying away.

Sapa-AFP

Bygone Olympics have offered presidents moments of political opportunity, or peril