By Jamie Coomarasamy
BBC News, Washington
To acquire the suffix "gate" - however fleetingly - an American political scandal usually needs to acquire a certain level of public awareness. "Naftagate" may be an exception.
The political debate comes amid the US's economic problems
For those who missed it, the term "Naftagate" was coined last month by Hillary Clinton's communications director, Howard Wolfson.
It refers to an apparent case of double standards in the Obama camp; the allegation that the Illinois Senator's top economics adviser told the Canadian government that the campaign's tough talk on the North American Free Trade Agreement (Nafta) would not translate into tough action once President Obama was installed in the White House.
Last week, the Clinton camp sent out an e-mail, asking fresh questions about the affair.
It is hardly surprising, then, that the news that Hillary Clinton's chief strategist, Mark Penn, had been acting as a cheerleader for a trade treaty with Colombia - a deal which she publicly opposes - was so damaging.
It wasn't just the conflict of interest, but the subject of the strategist's moonlighting which made it such an offence; an act of hubris, which resulted in the long-time Clinton adviser's removal from the front line of her campaign.
The Pennsylvania primary on 22 April approaches amid deepening economic uncertainty in the country.
Started on 1 Jan 1994, full implementation 1 Jan 2008
Allows free trade between US, Canada and Mexico
Side agreements regulate environment, labour
Critics say 1m US manufacturing jobs have been lost
Last week, it was announced that 80,000 American jobs were lost in March - the highest monthly figure for five years.
It is the context in which both Senators Obama and Clinton are pledging not to reject free trade but to temper aspects of treaties, such as Nafta, which - according to them - hurt American interests and cost Americans jobs.
Whatever the practical challenges of trying to renegotiate Nafta, or, indeed, the truth of its negative impact on the US economy, criticism of free trade seems to strike a particular chord in blue collar, Rust Belt states, such as Pennsylvania and Ohio, which have been shedding manufacturing jobs over the past few years.
It is no coincidence that the Clinton campaign's Howard Wolfson used the term "Naftagate" in the run up to last month's Ohio primary, which was eventually won convincingly by the former First Lady.
With her rival gradually accumulating pledges of support from the Super Delegates - the members of the party hierarchy who look set to decide the outcome of the nomination race - she badly needs a similar result in Pennsylvania.
Her team will be anxiously studying the opinion polls over the next few days, to see what effect - if any - the Mark Penn controversy has had on those working class voters, on whom she is depending for victory.
For the Obama team, it is an unexpected opening; one which, they hope, could help them pull off a major upset on 22 April.
An end to import tariffs on key staples provoked Nafta protests in Mexico
On the Republican side, it is a different story. The party's presumptive nominee for president, Senator John McCain, is an enthusiastic supporter of free trade and echoes President Bush's traditionally conservative view on the subject.
He will be pleased that, a day after Mr Penn resigned, Mr Bush issued a challenge to Congress, which is controlled by the Democrats, by sending the Colombian treaty to Capitol Hill for ratification.
Whichever Democratic candidate eventually secures the party's nomination, then, Americans will have a real choice on trade policy in November's general election.
Trade wasn't always such a partisan issue, of course. It was, after all, President Bill Clinton who signed Nafta into law in 1993 - despite what the Clinton campaign insists was the lukewarm support of his wife.
Support which appears to be growing cooler by the day.