WASHINGTON: US presidential candidates historically steer to the political middle once nominated, but Democrat Barack Obama’s unabashed grab for centrists American voters has further opened the door to Republican claims his message of change only applies to the positions he has taken in the past.

Perhaps most damaging was on Thursday’s statement in North Dakota, where he said he would reassess his stand on the Iraq war after he visits the front later this summer for briefings from American military commanders. Republicans tried to play that as an expedient political flip flopa signal Obama was moving away from his vow to withdraw all combat troops within 16 months of taking office, a defining issue of his campaign.

Obama quickly said that wasn’t the case but the Republicans rushed in with a critical broadside.

There appears to be no issue that Barack Obama is not willing to reverse himself on for the sake of political expedience,” said Alex Conant, a spokesman for the national Republican Party. Obama’s Iraq problem undermines the central premise of his candidacy and shows him to be a typical politician.”

But that’s not all. Obama has spoken out for the death penalty and against strict gun control. He’s backed new rules allowing government eavesdropping on terror suspects and called for giving more government money to religious groups that tackle social ills.

As with the war, critics on the right accuse Obama of adopting those positions in a cynical sprint to the political centre even a bid to plant his flag in territory typically held by Republicans.

But supporters say the Illinois senator is tacking smartly centre ward, driven on a course set by his fundamentally moderate political philosophy.

Others see a bit of both at work since Hillary Rodham Clinton suspended her campaign last month when Obama racked up the delegates need for nomination.

While Republican John McCain, too, is shifting to the centre, Obama’s recent tacticsthe issues he’s chosen to centrepiece and what he’s said about them stand in far greater contrast.

It’s a bit of a tightrope walk, but Obama appears to be relying on a safety net increasingly solid Democratic Party support coupled with a significant national distaste for the Republican administration of President George W Bush.

The latest Gallup Tracking Poll shows the Democrat ahead by only four percentage points, 47-43, perhaps reflecting voter confusion or refusal to wholeheartedly back him because his positions appear in flux.

The most important thing in politics is your brand,” says Matthew Dowd, a former strategist for President George W Bush. Obama’s brand is that he will be a different kind of politician. It’s a brand he’s built up over that past year and a half. But he’s dented that brand in recent days.”

That’s certainly been the case with the left wing of the Democratic Party, particularly over the candidate’s change of heart over punishing telecom companies that spied on Americans’ phone and internet communications for the Bush administration.

Obama initially said that he would block a reauthorisation of the Patriot Act, the bundle of anti-terrorism measures first passed by Congress after the Sept 11 attacks, if it forbade prosecution of those communications companies.