WASHINGTON, April 7: Hillary Clinton’s uphill quest to beat Barack Obama to the Democratic presidential nomination stuttered on Monday after her top aide quit over a firestorm sparked by his lobbying ties to Colombia.

The gruff political strategist had been blamed by some other Clinton insiders for her failure to quash Mr Obama’s challenge, and a message which cast her as a voice of experience, allowing her rival to claim the mantle of change.

Mr Penn quit after admitting he erred by meeting, in his capacity as a Washington lobbyist, Colombian diplomats who backed a trade deal with the United States that Hillary Clinton opposes.

The Obama camp hit out at Ms Clinton, arguing she had duped Democratic primary voters in Ohio last month, by hammering free trade pacts on the campaign trail, while her top aide was lobbying on behalf of the Colombia deal.

“I think there are issues associated with this. I’m not ... you can use the word ‘hypocrisy’ but there are certainly questions that arise from this,” said top Obama strategist David Axelrod on MSNBC.

Penn is a top executive in US public relations firm Burson-Marsteller, who has his own consulting firm, and is a Clinton family loyalist who helped plot the former first lady’s triumphant 2000 New York Senate campaign.

His thick contacts book was one of the factors that prompted Mr Obama to claim Ms Clinton’s White House bid was fueled by a bankrupt Washington political system that had failed the American people.

Mr Penn’s departure was announced late on Sunday in a statement by Clinton campaign manager Maggie Williams.

“After the events of the last few days, Mark Penn has asked to give up his role as chief strategist of the Clinton campaign,” Williams said.

Williams herself only took over in February, replacing Patti Solis Doyle as campaign manager after an internal tumult in the face of pressure from repeated victories by Barack Obama.

Aides said Penn’s consulting company would carry on providing polling to Hillary Clinton’s campaign, as she struggles to catch up with the Illinois senator in the party’s intense White House race ahead of the November general election.

It was revealed last week that Burson-Marsteller was hired by Bogota to promote a free trade pact between Colombia and the United States -- a treaty which Ms Clinton has opposed.

Mr Penn said last week he had made “an error in judgment” in meeting the Colombian ambassador to the United States, Carolina Barco, on March 31, and said he would not make the same mistake again.

Colombia retaliated by firing Burson-Marsteller, saying in a statement that it “considers this a lack of respect to Colombians, and finds this response unacceptable”.

Burson-Marsteller’s work for Colombia raised conflict-of-interest questions for Hillary Clinton’s campaign, as she had feverishly worked to court working-class votes in states which believe free trade has hammered their manufacturing base.

In addition, when details of the Penn-Colombia meeting became public, some labour unions angrily called on Ms Clinton to fire Mark Penn.

Hillary Clinton triumphed in the Ohio primaries last month, in a victory credited with reviving her White House campaign, which polls suggested was based on backing from white, blue-collar voters attracted by her populist economic message.

She profited in Ohio by casting doubt on Barack Obama’s opposition to the North American Free Trade Agreement, after a meeting between an aide to the Illinois senator and Canadian diplomats came to light.

The alleged iniquities of free trade have become campaign fodder as Obama and Clinton battle it out on the way to the Pennsylvania primary on April 22.—AFP