Gloves are off in the fight to halt Obama

Accusations of plagiarism, charges that the candidate reneged on a promise over campaign finance, a supposed gaffe by his wife – anything now goes in the battle to halt Barack Obama's march towards the 2008 Democratic nomination.

His resounding victories in Tuesday's votes in Wisconsin and his birth state Hawaii – Mr Obama's ninth and 10th straight wins in the past fortnight – have left Hillary Clinton needing to sweep the primaries in both Ohio and Texas on 4 March to stay in the race.

It increasingly appears that only a major blunder by the Illinois senator, or a damning revelation, can deny him the nomination. His opponents – Ms Clinton in the primaries and John McCain, his likely Republican adversary in the general election – plainly feel that way. But, for the time being at least, nothing they have come up with is sticking.

The Clinton camp was the first to try, charging that her rival had plagiarised some rousing lines delivered by Deval Patrick, the black governor of Massachusetts, in 2006.

But Mr Obama brushed aside the accusation, noting that Mr Patrick was a close friend and that the borrowing was "no big deal". Wisconsin's voters evidently agreed.

More serious perhaps was a claim this week by Michelle Obama that, "for the first time in my life I am really proud of my country". Ms Obama, a 44-year-old Harvard-trained lawyer, has a reputation for speaking her mind, but the Clinton and McCain campaigns alike have seized on her remark as evidence of ingratitude and even racism.

"I don't know about you, I'm very proud of my country," Cindy McCain, the Republican candidate's wife commented when asked about Ms Obama's words.

At the same time Mr Obama seems to be backing away from an earlier promise to use public financing in the final phase of the election, if he won the Democratic nomination. Mr McCain says the episode proves that however uplifting, Mr Obama's rhetoric is no more than empty words.