As American voters go to the polls to select the Republican and Democratic presidential nominees, few are aware that their right to vote in private - at least in the workplace - may be in danger.

It seems too bizarre to be true, but union bosses want to end secret ballot elections, and many members of Congress are willing to go along. If they succeed, more than 100 million workers would lose their right to a private vote on whether to join a union.

Secret ballot elections are a fundamental American right. They ensure that every voter expresses his or her choice without peer pressure or harassment and that the choice of the majority prevails. That's why we use private ballots to elect the president and members of Congress. It's also why American workers choose to join - or not join - unions in secret ballot elections.

When Congress passed the National Labor Relations Act in 1935, it allowed unions to organize workplaces without elections. Organizers asked workers to sign union cards, and the union became their representative once a majority of workers publicly signed on. In this "card-check" process, workers had no privacy at all - organizers knew exactly who was on their side. Union membership, not surprisingly, skyrocketed.

Many workers signed union cards because they wanted a union. Others were pressured into joining. Union intimidation, threats of violence and peer pressure caused many workers who didn't want to join to sign union cards anyway. Public outcry at such abuses led to bipartisan legislation providing workers with the protection of a secret ballot.

Today, when union organizers collect enough signed union cards at a workplace, the government supervises a secret ballot election. After a short campaign the workers vote on joining in privacy. Neither the union nor the employer knows how an individual worker actually voted. That's how democracy should work.

These private votes have served workers well. Companies cannot credibly threaten to fire union supporters because they don't know who voted for the union. But workers are also free to sign cards handed to them by union organizers at their homes at night, then express their true wishes in the voting booth.

To the dismay of union organizers, this often happens. Union organizing manuals caution that many workers sign union cards just to "get the union off my back." Unions win over three-fifths of private elections, but they would like to win far more.

The union movement has fallen on hard times. Fewer private sector workers belong to a union now than when the National Labor Relations Act took effect. Unions made more economic sense in the manufacturing economy of the 1950s than in the 21st century information economy.

Union corruption, political activism and misuse of members' dues have turned off millions more Americans. By a 3-to-1 margin, polls show that nonunion workers are happy to stay that way.

Rather than reform to become relevant to today's workers, union bosses are lobbying for legislation to make it harder for workers not to join. Their No. 1 legislative priority is the misnamed "Employee Free Choice Act."

This little-known act would replace secret ballot-organizing elections with card-check organizing. It takes away workers' right to a private vote on joining a union and forces them to make that choice in public.

If it can be called a choice. In an election, workers can vote yes or no, but with card-check, workers cannot vote against the union. Workers can only refuse to sign the card, which simply means "not now."

If the worker doesn't sign on today, the organizers will return tomorrow … and the next day … and the next. At times, workers are threatened with repercussions for not joining. With card-check, workers cannot privately say, "I don't want Jimmy Hoffa and the Teamsters to represent me."

Some 105 million American workers would lose their right to a private vote under the "Employee Free Choice Act." It has nothing to do with employee free choice and everything to do with increasing union membership.

Yet many politicians are on board. Mandatory union dues fund a substantial union political machine, and organized labor has made it clear that any politician who wants union support must oppose secret ballot elections.

A majority of the House of Representatives, the Senate and every major Democratic presidential candidate have agreed to this Faustian bargain. The 2008 elections could lead to a Congress and a president willing to do away with voting privacy.

Even as Americans cast private votes to select the next president, few workers know that their right to a secret ballot is on the line.

James Sherk is a policy analyst in the Center for Data Analysis