Opinion | US presidential election: the power of the Asian vote

At this time four years ago on the streets of northern Virginia, an influential Asian-American heartland in a key electoral swing state, there was a distinct smell of death surrounding the campaign of the veteran Senator John McCain, the Republican White House hopeful.

Representatives of Asian-Americans for Obama - ethnic Chinese, Koreans, Vietnamese and Filipinos - were taking the suburbs by storm in a way not seen before. With flags, banners and rallies, they created a palpable presence on behalf of the young Chicago senator then vying to become the first black president of the United States. More importantly, too, they were going door-to-door in suburbs both rich and working-class, making sure their neighbours were not just energised, but registered and planning to turn out to vote.

And vote they did. Obama took the presidency, in part thanks to a historic win in the southern state. It marked the first time Virginia had voted Democratic since electing president Lyndon Johnson in 1964, and never before had Asian-Americans had such a targeted impact on a US election.

But four years on, it is a different story. Virginia is once again in play and the campaign of Republican contender Mitt Romney is fired up after four tough years for the Obama administration.

McCain, it should be remembered, was attempting to follow the failed eight-year presidency of the Republican George W. Bush, amid a collapsing economy and the mire of Iraq. As one professional Republican staffer said at the time: "I never thought I would see the day when it is embarrassing to tell people in Virginia that you are a Republican, but it is upon us. I go to weddings now, and I don't tell people what I do." No one talks like that now.

Unlike McCain, Romney has momentum. His team is showing that they have learned the lessons of Obama's earlier success and have built their own formidable Asian-American operation in Virginia.