Electing a corporate board isn t typically a dramatic affair. Most individual shareholders don t bother to vote, and most of a company s candidates are elected with an overwhelming majority. In 2009, for example, only 0.3% out of the 30,000 directors reviewed by the Corporate Library, an independent research firm, failed to get majority support.

Next year could be a different story. New rules approved Wednesday by the Securities and Exchange Commission put shareholders on more equal footing during the nominating process and could effectively swing open the boardroom door.

The new rules provide shareholders with a tool advocates have been seeking for years: proxy access. Now, a shareholder or group of shareholders who want to nominate their own candidate for a corporate board can get that candidate s name on the company s proxy materials, rather than having to reach out to other shareholders at their own expense.

That expense can be significant. Corporate campaigns costs can vary from $250,000 to multiple millions, according to James McRitchie, a shareholder advocate who runs the website CorpGov.net.

When Eric Jackson, an activist investor and the founder of Ironfire Capital, wanted to nominate alternative director candidates to Yahoo (YHOO) board in 2007, he was told the campaign would cost at least a million dollars in lawyers fees, mailing costs and other expenses.

Companies still won t have to include on their proxy ballots every candidate a shareholder suggests. Under the new rules, only an investor or group of investors who have held at least 3% of a company s shares continuously for at least three years can get their candidates names on the company ballot.

We re talking about having shareholders hold massive amounts of stock for a long amount of time, says Doug Gates, vice president of marketing at MoxyVote, a web site that aims to organize retail shareholders to vote their proxies.

The new rule will eventually apply to all public companies, but it will not go into effect for small firms with a public float of less than $75 million for another three years.

The delay has drawn some concern from shareholder advocates. Small companies are more likely to suffer from serious governance problems, says Andrew Shapiro, the president of Lawndale Capital Management, an activist investment firm. Because the small-company cutoff is defined by public float, not market cap, companies in which insiders hold a large portion of the stock will have an easier time slipping under the bar, even though they re more likely to have boards that are insular, dysfunctional and completely unresponsive, Shapiro says. A firm could have a $110 million market cap but be considered a small company if insiders owned 35% of the shares, for example.

Business interests remain opposed to proxy access, and the SEC itself was split 3-2 on the issue, with Republican commissioners voting against the new rules. "Commissioner Kathleen Casey called the rule fundamentally and fatally flawed and said it empowers institutional shareholders at the expense of retail shareholders.

David Hirschmann, the president and chief executive of the U.S. Chamber of Commerce s Center for Capital Markets Competitiveness, said in a statement that proxy access would serve only special interest activist investors, like union pension funds, and harm individual shareholders, who will not be able to use the new rights.

Other critics said moving on proxy access before reforming other aspects of the proxy voting system was premature. The new rule puts the cart before the horse, says John Olson, a founding partner at the law firm, Gibson, Dunn & Crutcher, who advises companies on corporate governance issues. Companies currently have to go through middlemen to communicate with the retail shareholders who are most likely to have a long-term view, Olson says. Reforms to make it easier for companies to contact their individual shareholders should have come before changes that expose companies to more contested director elections, he says.

Some said worries about special interest groups were overblown. Shareholders would have to not just nominate candidates, but elect them, for concerns about special interests to be a problem, says Michael Littenberg, a partner at the law firm Schulte, Roth & Zabel who focuses on corporate governance issues. A candidate representing real narrow niche interests would be unlikely to win majority shareholder support, he says.

At MoxyVote, left-leaning political or social organizations like the Teamsters or PETA make up the majority of the site s registered groups, but the greatest voter turnout has come when people vote their pocketbooks, Gates says. Investors holding 11.5% of outstanding shares at On2 Technologies, for example, organized through the site to reject a buyout offer from Google (GOOG), until the offer was raised by more than $25 million. And even board members supported by passionate advocates like PETA would have to represent the long-term interests of shareholders, Gates says.

The new rule is unlikely to flood the ballot because there aren t many investors who can meet the 3%-for-three-years threshold, says McRitchie, the shareholder advocate. Hedge funds will be unlikely to hold the stock long enough, and socially responsible investing firms will have a hard time cobbling together a large enough block of shares, he says. Union pension funds would be the most likely to take advantage of proxy access, he says.

Large mutual funds typically don t want to be associated with shareholder activism, Jackson says.

For individual investors, the new rules mean that the proxy statement they receive in the 2011 proxy season may not be business as usual, Littenberg says. Retail shareholders will want to read the proxy statement a little more closely.

Reading a proxy statement at all might be a big step for many investors. Right now, the vast majority of retail shareholders who get their ballots in the mail throw them away and just don t vote, Gates says. The fact that retail investors are sacrificing a few trillion dollars worth of influence a year is ridiculous, especially in a country where money talks.