Conventional wisdom in Washington says Barack Obama has so far come off worse in his increasingly fissile exchanges with Hillary Clinton on national security.
At the latest Democratic candidates' debate on last Tuesday night, Clinton was joined by Christopher Dodd and Joe Biden, the senators for Connecticut and Delaware, in attacking Obama's alleged callowness and naivety.
They highlighted the apparent inexperience behind Obama's comments recently that as president he would rule out the use of nuclear weapons in Afghanistan and Pakistan while at the same time brandishing the possibility of pre-emptive military strikes on Al Qaida bases in Pakistan.
Obama's much-quoted line about using "actionable" intelligence to target the Al Qaida havens in Pakistan even sparked a bout of burning US flags in Pakistan as well as protests from Islamabad.
"Words mean things," Dodd told a 17,000-strong crowd of union workers in Chicago. "We have to be very careful about language in terms of the danger and harm it can do to our nation."
Clinton said: "You can think big, but remember you shouldn't always say everything you think if you're running for president, because it has consequences across the world." Predicting that a strike on Pakistan would bring radical Islamists to power, she added: "We don't need that right now."
The 45-year-old freshman senator from Illinois has also become a target of the rival Republican presidential field.
During their latest debate, Massachusetts governor Mitt Romney made fun of the apparent contradiction between Obama's pledge to strike Al Qaida in Pakistan while also promising to talk to foreign dictators within a year of taking the White House (the trigger for round one of the Clinton-Obama feud which prompted Clinton to brand her rival "inexperienced and frankly naive").
"I mean, in one week he went from saying he's going to sit down, you know, for tea, with our enemies, but then he's going to bomb our allies," Romney said to laughter from the Republican audience. "He's gone from Jane Fonda to Dr. Strangelove in one week."
All of which might have pushed another candidate into retreat. Yet to judge by the barrage of Obama campaign e-mails, memos and statements, the Obama camp believes that keeping the dispute alive serves their purposes well. Advisers to Obama say that his clash with Clinton highlights two of his strengths.
First, it gives Obama an opportunity to play on his status as a "Washington outsider" - one of Clinton's biggest vulnerabilities, given her many years in DC.
Last Tuesday, Obama reminded people of the fact that he opposed the Iraq war from the beginning, unlike Clinton - and Biden and Dodd - who in 2002 voted in favour of a resolution authorising Bush to use force. That line elicited cheers at the debate.
"Look, I find it amusing that those who helped to authorise and engineer the biggest foreign policy disaster in our generation are now criticising me for making sure that we are on the right battlefield and not the wrong battlefield in the war against terrorism," he said.
Obama also drew blood last month when he inferred that a Clinton administration would be "Bush-Cheney lite".
Went too far
The second purpose, say Obama advisers, is to make sure that voters understand their candidate is not a - liberal pushover who cannot be trusted to be commander-in-chief.
Many Democrats believe Obama went too far in illustrating that point when he criticised the Bush administration for having pulled back from a potential 2005 strike on an Al Qaida meeting in Pakistan's border areas.
Others, including the conservative opinion pages of the Wall Street Journal, which called Obama a "neocon", seemed to enjoy it. "Anyone who wants to run to the right of Rummy [Donald Rumsfeld, the then defence secretary] on counter-terrorism can't be all bad," it said.
There is, however, a further but unacknowledged motive for Obama's growing combativeness - the urgent need to check Clinton's widening opinion poll advantage.
The latest gives the former first lady a 20-point lead over him. If that persists, Clinton could gather a commanding momentum as the primaries approach in January.
"A lot of the apparent - foreign policy differences between the main Democratic candidates are in reality minuscule to non-existent," says an adviser to John Edwards (who is running third in the field), although he was not speaking on behalf of Edwards's campaign.
"That is why I fear this campaign is going to get increasingly personal as it goes on."
