The rightwing Swiss People's Party and the Greens look set to make the biggest gains in Sunday's parliamentary elections.
The centre-left Social Democrats suffered a major defeat, according to a survey based on partial results and commissioned by swissinfo's parent company, the Swiss Broadcasting Corporation.
Final results as well as a breakdown of seats for the House of Representatives are not expected before Monday morning.
The People's Party took 28.8 per cent of the vote in the elections for the House, up 2.1 per cent on 2003, according to the gfs.berne polling institute.
If confirmed the People's Party posted the best result among the four governing parties since 1919 and could win 62 of the 200 seats in the House.
The Social Democrats appear to have suffered the biggest loss, losing nine seats and taking 19.3 per cent of the vote, down from 23.3 per cent four years ago.
The Radicals lost five seats as their share of the vote dropped 1.5 per cent to 15.8 per cent, while the other centre-right party, the Christian Democrats, recorded slight gains, winning three seats and 14.7 per cent, up 0.3 per cent.
These four parties have held more than 75 per cent of the seats in parliament for decades.
The true winners of the 2007 elections could be the Greens. They are forecast to boost their number of seats in the House to 19, from 14. Their share of the vote increased to 9.6 per cent from 7.7 per cent.
The Greens also won their first seat in the 46-member Senate. Run-off elections will be held in eight of the country's 26 cantons.
The president of the People's Party, Ueli Maurer, said his party was committed to working for consensus in the cabinet in an apparent reversal of its confrontational style in the election campaign.
The Social Democratic Party admitted defeat, saying it had failed to convince voters with a programme of social and environmental issues.
Mud-slinging in the run-up to election day increased voter interest slightly, and turnout was estimated at an above-average 48 per cent.
The campaign was dominated by controversy over Justice Minister Christoph Blocher and his People's Party's hard-line stance on immigrants and crime.
A People's Party poster campaign depicting white sheep kicking a black sheep off a Swiss flag drew worldwide media attention and criticism from the United Nations.
Other issues, such as climate change, taxes, social security and unemployment were pushed into the background.
The increasingly aggressive campaign escalated into violence at a rally in the capital, Bern, two weeks ago.
Police clashed with leftwing militants who tried to interrupt a public gathering of the People's Party and their supporters.
For the first time in nearly 50 years the parliamentary elections focused on the personalities of cabinet ministers.
Traditionally they act neither as party leaders nor are they directly accountable to their political parties.
This is widely believed to have been the most expensive election campaign in Swiss history with parties spending at least SFr50 million ($42 million).
No detailed figures are available, and Switzerland does not have a transparency law on the financing of political parties.
More than 3,100 candidates, including 44 Swiss expatriates, ran for seats in parliament for the next four-year term.
The two chambers will choose the new cabinet at a joint meeting in December.
Voters chose the 200 members of the House of Representatives and most members of the Senate for the next four-year term.
The four main parties – People's Party, Social Democrats, Radicals and Christian Democrats – control more than 75% of the seats in parliament and share the seven cabinet posts.
An alliance of Greens and other leftwing parties is the biggest opposition grouping.
Both houses of parliament will meet on December 12 to elect the new cabinet.
Seats in both houses of parliament - 2003 elections:
People's Party: 63 seats
Social Democrats: 61 seats
Radical Party: 50 seats
Christian Democrats: 43 seats
Greens: 13 seats
Others: 16 seats
Total: 246 seats
Swiss Abroad Candidates
A total of 44 Swiss expatriates were standing for a seat in the House of Representatives - three times more than in 2003.
According to the Organisation of the Swiss Abroad (OSA), between 30% and 50% of Swiss living abroad who are registered to vote were expected to exercise their right.
Over 110,000 Swiss abroad were registered to vote.