Washington - The issue of patriotism has been placed at the forefront of the US presidential campaign this week as the United States celebrates its independence. Both Democratic candidate Barack Obama and his Republican rival John McCain have aggressively pushed back on questions of their service or dedication to the United States.
Obama, who would be the first African-American president, has had the most serious problem. Since his campaign's inception in early 2007, the Illinois senator has been the target of a series of false rumours that raise suspicions of his loyalty to the country.
Initially spread through the internet, the claims include that he has refused to recite the US pledge of allegiance - a practice in most US schools - and will not wear a US flag-pin.
Another repeated claim is that he is a Muslim, and even that he attended a radical Islamic madrassa school during a four-year spell in Indonesia as a young child.
Obama is in fact a Christian, though he comes from a non-religious family and was only baptized as an adult. His father was a Muslim from Kenya but abandoned the family when he was aged two. Obama was raised mostly in Hawaii by his mother and grandparents.
The internet rumours have slowly turned into a regular narrative that can be heard in neighbourhoods across the country. Some of the talk is earnest, others make passive references - a teenager in Washington joking to friends that Obama sought "Jihad on America," for example.
Obama's campaign has become increasingly concerned, launching a website - www.fightthesmears.com - that is dedicated to rebuffing any and all falsities.
The current rumour being knocked down is that Obama was not born in the United States. The site provides a picture copy of his birth certificate - he was born in Hawaii - and encourages supporters to send their own emails to counter "right-wing smears."
Obama himself has become occasionally indignant at mainstream reporters who have raised the smears on the campaign trail, but he took up the issue in detail earlier this week in a broad speech on the meaning of patriotism.
"At certain times over the last 16 months, I have found, for the first time, my patriotism challenged - at times as a result of my own carelessness, but more often as a result of a desire by some to score political points and raise fears about who I am and what I stand for," Obama said.
"I will never question the patriotism of others in this campaign, and I will not stand idly by when I hear others question mine," he said at a rally Monday in the aptly named town of Independence, Missouri.
McCain is no stranger to smears himself, after a bitter 2000 campaign for the Republican nomination against President George W Bush. Anonymous opponents of McCain famously spread rumours that the Arizona senator had fathered an illegitimate child.
McCain, regarded as a war hero after being held captive and tortured for five years in Vietnam, launched his own "truth squad" this week to counter any efforts to denigrate his long military service record.
The move came after former NATO commander Wesley Clark suggested McCain's military experience did not qualify him to be president.
"I don't think riding in a fighter plane and getting shot down (in Vietnam) is a qualification to be president," Clark said on Sunday, sparking a furore among McCain supporters who demanded an apology.
Obama rejected Clark's comments and has regularly said he has the highest respect for McCain's military service, but both candidates' sensitivity highlights the importance that patriotism questions can play in US politics.
A late attack on the military service record of 2004 Democratic candidate John Kerry - a war hero in his own right - was in part credited with costing him the general election against Bush.
Obama turned the issue back on voters Wednesday, calling for Americans to engage more in public service to their country as they reflected on US independence on Friday.
"Loving your country shouldn't just mean watching fireworks on the fourth of July," Obama said. "Loving your country must mean accepting your responsibility to do your part to change it."
