If, like me, you think of Massachusetts as the sort of place where they weigh the Democratic vote, rather than count it, you'll be surprised to read that the state's junior seat in the Senate [2] could be won by an anti-tax, socially conservative Republican.

But with six days to go until voters head to the polls, commentators are taking seriously the possibility that the Republican Scott Brown could replace the late Ted Kennedy.

The speculation was triggered by a series of polls [3] putting Brown within touching distance of the Democratic candidate, Martha Coakley. Coakley's lead has fallen from 30 per cent in October to 15 per cent at the start of this month and has now, according to one poll, evaporated all together.

Brown's progress is even more striking considering he lies well to the right of where successful Massachusetts Republican candidates usually reside. In the past, the party has fielded fiscally conservative but socially liberal candidates, such as the former governer Mitt Romney, whose support for gay rights dogged his campaign [4] for the GOP presidential ticket.

But not only does Coakley oppose same-sex marriage, he supports waterboarding terrorism suspects and has vowed to destroy health-care reform.

Few psephologists predict a Republican victory, and most commentators have dismissed the poll showing Brown ahead by 1 per cent as an outlier. But the hype behind his campaign says much about the desire of the right-wing media to write off Obama's presidency as a failure and to suggest that the Democrats will suffer huge losses in this year's midterms.

Should Brown pull off a victory against the odds, he would be the first Republican to do so since 1947. He has vowed, if elected, to be the "41st" senator: the one who could tip the Senate against health-care reform.

It would be grim indeed if Brown replaced Kennedy and defeated what the late senator described as "the cause of my life".

Follow the New Statesman team on Twitter [5]