IT IS NOT the sort of thing that moderates are supposed to do. Three days before the Democrats meet in New Hampshire for the state’s presidential primary election on February 11th, Joe Biden released an advertisement attacking Pete Buttigieg for his lack of experience (Mr Buttigieg is the former mayor of a city of 100,000 people in Indiana), and reminding voters of his own CV as Barack Obama’s vice-president. Perhaps it was Mr Biden’s poor performance in Iowa the week before that put him on the offensive. Or maybe the Granite State’s chilly winter nights have frozen the heart of “Uncle Joe”. Either way, the ad—one of the most negative of the Democrats’ primary campaign so far—laid bare two facts about Mr Biden’s campaign: he is flailing, and he sees Mr Buttigieg as his chief competitor.

For months Mr Biden’s campaign had a veneer of inevitability to it. Former vice-presidents are typically shoo-ins for presidential nominations, if not the presidency. But for Mr Biden, that illusion was shattered in the Iowa caucuses on February 3rd. He came in fourth place with only 15% of the vote, bested by Elizabeth Warren by three percentage points, beaten by Mr Buttigieg by six, and ten behind Bernie Sanders.

Mr Buttigieg will probably survive the assault. Voters in New Hampshire are likely to see the advertisement for what it is: a candidate in distress gasping for air. “Being a First in the Nation Primary voter is a huge responsibility,” writes Ray Buckley, chair of the state’s Democratic Party. “When you meet a voter at a campaign event, chances are they have met at least a handful of candidates.” In other words, nobody will be surprised to hear about Mayor Pete’s youth or Mr Biden’s experience.

Since winning the plurality of pledged delegates in Iowa, Mr Buttigieg has shot up in the polls. This is a common pattern historically; Iowa’s winners typically enjoy double-digit bounces in national polling over the next few months. The Economist’s average of polls finds Mr Buttigieg climbing fast in New Hampshire. Polls released over the weekend pushed his support from 16% to above 20%. He is favoured to finish second behind Mr Sanders, whose numbers are currently hovering near 30%.

Mr Sanders remains the strongest candidate in New Hampshire. He has topped the polls there for most of the past month. Edith Tucker, a state representative from the northern county of Coos, says that voters credit him for his authenticity: “He gives the same speech, but you feel that he’s letting it all out. And he’s not pandering to you.” Consistency has been one of the key points in his campaign, and his embrace of far-left policies and democratic socialism have not turned off many voters.

Mr Sanders’s biggest strength is not his platform or his charm, however, but the long list of candidates on offer to Granite-state voters. If polls are right in giving him nearly 30% of the vote, that would be less than half the share he secured in the 2016 Democratic primary in New Hampshire. But, as in Iowa, a fractured opposition makes it hard for any challenger to topple Mr Sanders.

This lays bare Mr Biden’s motivation for attacking Mr Buttigieg: if he does not soon establish himself as the clear moderate alternative to Mr Sanders, he will not stand a chance of winning the nomination. While the centrists struggle to coalesce around a single candidate, Mr Sanders can rack up wins that attract favourable media coverage and campaign contributions.

It is still possible that no candidate at all wins an outright majority of delegates. According to the election handicappers at FiveThirtyEight, a data-journalism website, Mr Sanders is currently favoured to win the nomination. But winning bare pluralities will not be enough to put him on top; his average predicted delegate haul is only about 1,700 of the 1,990 pledged delegates needed to win the nomination.

Mr Biden’s path to the nomination also looks tough. His original campaign strategy relied on surviving early defeats by pulling off big wins in states that vote later in the primary calendar. But this prospect has recently declined. According to The Economist’s aggregate of primary polls, the former vice-president is now tied with Mr Sanders in the Nevada caucuses, the third contest, and has fallen from 40% to 30% in South Carolina. Mr Buttigieg and Ms Warren will have trouble winning a majority of delegates, as both fare badly with non-white voters, who make up a larger share of the electorate as the campaign goes on.

The chances of any of these candidates reaching a majority is further complicated by the rise of Mike Bloomberg, the billionaire former mayor of New York who has poured hundreds of millions of dollars into the race and now scores above 10% in national polls. Although he has not campaigned in the first four states, he could do well on Super Tuesday. Mr Bloomberg is performing strongly in Texas and California, states which together account for 16% of the pledged delegates. But a good showing by Mr Bloomberg would mean even greater fragmentation among the delegates. As the candidates make their final preparations in New Hampshire, a contested convention, in which no candidate has enough delegates to win outright, is looking ever more likely.

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