The billionaire industrialist's right-wing Swiss People's Party (SVP) is expected to win the most votes in elections on 21 October, rounding off a campaign that the United Nations described as blatantly racist.
The party has depicted Switzerland as a society under siege from immigrants who have scant regard for the country's laws and customs.
Many voters appear to be impressed by the skilled oratory of Mr Blocher, 67, seeing him as the epitome of a stern leader stepping forward to safeguard Swiss values.
Mr Blocher, currently justice minister, was quick to make political capital out of rioting that erupted at an SVP election rally in Bern. Left-wing protesters clashed with police, adding to the unusually edgy atmosphere of this Swiss election.
"It's obvious that the biggest party in Switzerland can no longer go to the federal square," Mr Blocher told a cheering crowd of supporters.
Consensus challenged
The SVP is currently pushing for a law that would give authorities the power to expel entire families of immigrants if one member is found guilty of a violent crime or of an offence such as drug dealing or benefit fraud.
Swiss row over sheep poster
A poster linked to the campaign, featuring three white sheep ganging up on a black sheep, was condemned as racist by opposition groups and the UN.
The party insists its poster does not reflect its policy towards immigrants at large - merely those with criminal records.
Switzerland's citizenship laws - among the toughest in the world - mean roughly 20% of the population are classed as foreigners, even though many were born in Switzerland.
It is not only Switzerland's immigrants who view Mr Blocher with deep distrust.
He is also unpopular among many of his fellow politicians and among voters in the country's Francophone west.
They regard Mr Blocher's combative manner as a threat to the delicate consensus that has traditionally dictated the shape of Switzerland's government.
Blocher's rise
The decades-old system of dividing cabinet responsibility between the top parties, known as the "magic formula", received its first jolt in 2003.
An election win that year gave the SVP two seats instead of one, placing it on a par with the Socialists.
Mr Blocher has been a dominant force since as early as 1986, arranging campaigns and referendums to keep Switzerland out of international organisations.
And he has almost single-handedly turned the SVP from a docile, eastern rural party into a provocative, isolationist national force tapping into many of the fears and aspirations of ordinary Swiss.
Mr Blocher's main support is in the Zurich area - the SVP's German-speaking heartland.
He became leader of the party in Zurich canton in 1977 after gaining a reputation as a fiery public speaker, and two years later was elected to the national parliament.
Referendums
While pursuing his political career, he has also become a prominent industrialist.
In 1983 he bought the Swiss plastics and polymers giant EMS Chemie.
He has since made a fortune with the company, recently estimated by US business magazine Forbes at $1.4bn, and is the ninth richest person in Switzerland.
Mr Blocher first rose to fame 17 years ago, when he founded a lobby group, the Campaign for an Independent and Neutral Switzerland (CINS).
BLOCHER'S REFERENDUM CAMPAIGNS
He led and financed the campaign that year against United Nations membership, garnering the support of three-quarters of Swiss voters.
Since then, the SVP has used the country's unique referendum system to counter government policy over such issues as European integration and immigration.
Mr Blocher's high profile led to a surge in support for the SVP in 1999 elections, with the party taking 22.5%.
He was seen as a star turn at election rallies. The party faithful, farmers, businessmen and pensioners, turned out in droves to hear him speak.
Although he insisted he was not racist, Mr Blocher did begin to attract extreme right-wing support.
He was described at the time by left-wing journalist Jean Martin Butner as "the guy who just has the match and isn't there when the fire breaks out".
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