Two pillars of Swiss nationhood are being tested Sunday -- citizenship and the post office.

In referendums, the cornerstone of Switzerland's finely honed system of direct democracy, voters are to decide whether to loosen the Alpine country's tough rules on citizenship for foreigners, and whether to block their government's cost-cutting campaign to shut post offices, historically the glue that has held Swiss society together.

The nastier of the campaigns concerns the government's proposal to change the constitution's rules on citizenship. Under such slogans as "mass giveaway" and "don't sell out Switzerland," opponents of the measure are portraying Osama bin Laden's photo on a Swiss ID card and have put up posters showing black and brown hands reaching for a pile of Swiss passports.

On the other side of the debate, some parties have run full-page newspaper ads denouncing the campaign as racist and "spreading unjustified fear and hatred."

The changes, which voters are expected to approve, reflect a recognition that Switzerland, long accustomed to homogeneity within its Alpine ramparts, is becoming a multicultural society.

About one in five of the 7.2 million people living in Switzerland is foreign born. Foreigners have to wait at least 12 years to receive citizenship. The Swiss-born children -- and even grandchildren -- of immigrants do not automatically qualify.

Under the proposed changes, the grandchildren would get citizenship automatically, and children born in Switzerland -- or at least raised there from an early age -- would quickly become eligible.

The post office campaign, though more benign, appears more divisive, with polls showing no clear majority either way.

To the outside world, Switzerland's banks are its symbol of fiscal steadfastness. But to ordinary Swiss, that role falls to the more than 3,300 post offices. Virtually all bills sent to households include a form for payment at the post office counter. Retirees can collect their pensions there. Many Swiss have post office bank accounts and debit cards.

Switzerland has been privatizing its communications industry and closed 668 post offices over the past three years. But Swiss have objected in large enough numbers to amass the 100,000 signatures needed to force a referendum in hopes of halting the closures.