Umberto Bossi brought down Silvio Berlusconi's first government
Italy's centre-right leader Silvio Berlusconi won a return to power this week with a majority that - by Italian standards - looks very comfortable.
But he did so with the help of a formerly troublesome and often controversial right-wing ally, the Northern League.
The populist party almost doubled its vote, winning more than 8% nationally, and is expected to have several ministers in the new government.
That has led to concerns about what critics see as the party's overtly xenophobic stance, and questions over whether Mr Berlusconi will be "held hostage" by the League.
"Now we need reforms", Umberto Bossi, the party's colourful leader, told the newspaper La Stampa the day after the vote. "Otherwise we will lose patience."
For more than a decade, the party has been an uneasy partner with Mr Berlusconi's other major ally, a nationalist group led by Gianfranco Fini that draws much support from the south.
It was the League that toppled Mr Berlusconi's first administration in 1994, after less than a year in power.
The second time the media tycoon became prime minister, in 2001, the League repeatedly threatened to bring the government down once more if its policies were not given priority.
Ultimately, however, the League was loyal.
While some observers say that with more seats, the League could once more cause problems, others say the party has evolved into a more durable and astute political force.
It is unlikely, they say, to provoke the kind of collapse suffered by the centre-left government of Romano Prodi earlier this year.
"They've all got older and more mature - both Bossi and Berlusconi," said Sergio Romano, a political columnist and commentator.
"Quarrelling among themselves will damage their own victory. They've all seen what happened to Prodi, they will be very careful."
Mr Bossi has been less prominent since he was sidelined by a stroke in 2004, even though his outlandish comments have not dried up.
During the campaign he threatened to take up arms against what he said was the left's attempt to rig ballots.
But his relationship with Mr Berlusconi is now close.
"He's not a hostage. He's a friend," the League leader said of the prime minister-elect.
The League's campaign focused on what it sees as the waste, inefficiency and corruption of the political class in Rome.
That has always been a rallying call for the party, which became a significant force in the wake of the corruption scandals of the early 1990s as it attacked "robber Rome".
The League has led protests against migrants
It argued that Italy's prosperous north should stop subsidising its underdeveloped south.
Early on the League was secessionist, before modifying its demand to one of extensive autonomy for the northern territory of "Padania".
The anti-politics theme has been given a good airing recently, partly thanks to a best-selling book called The Caste: How Italian Politicians Have Become Untouchable.
The book details how the costs of politics have become grossly inflated over the past few decades.
Though the Northern League led the way in attacking the caste, the authors criticise League politicians for being lured into it despite their initial reforming zeal.
Mr Bossi says the support for his party in this election represented more than a protest vote.
"The north has sent a clear signal, it absolutely wants the country to change," he said.
The first measure the party will press for is "fiscal federalism", which would allow regions greater control over tax revenues.
Another of the League's big issues is immigration.
The party has played on economic and cultural fears in a country where this is a relatively new phenomenon.
This campaign poster tried to play on fears of immigration
Its position has often been expressed in crude terms, drawing charges of racism.
Mr Bossi triggered a storm in 2003 when a newspaper quoted him as saying that immigrants arriving in Italy by boat should be stopped by a cannon that "blows everyone out of the water".
The League leader said his views had been misrepresented.
Another of the League's top politicians, Roberto Calderoli, was forced to resign from the cabinet in 2006 after revealing a T-shirt on TV emblazoned with a cartoon of the Prophet Muhammad, originally published in Denmark, that triggered worldwide protests among Muslims.
In this year's campaign, one of the party's election posters displayed a drawing of an American Indian in a feathered headdress, accompanied by the slogan: "They suffered immigration: Now they live in reserves."
Martin Schultz, head of the Socialist group in the European parliament, said Mr Berlusconi's alliance with the Northern League represented a "real danger for Italy and for Europe".
But observers say that even the comments on immigration, while deeply unattractive, may largely be bluster, as the north relies on immigrant workers to power its economy.
"The League is a northern party and in the north there are fears about immigration," said Mr Romano.
"But then of course the north needs the immigrants and the League knows it."