Ask any of the presidential candidates about the disadvantages of running against an incumbent and they'll probably point out things like the White House Conference on Small Business.

It's no surprise, therefore, that President Carter has picked an election year to hold the first White House Conference on Small Business, an opportunity to win the hearts and votes of the nearly 80 million small business owners and their employes.

But the opportunity to woo the nation's small business community -- fast becoming one of the more potent political lobbies -- is not limited to incumbent presidents. The conference also will be a nice forum for incumbent congressmen.

The conference is intended to address issues of interest not only to the country's small business people, but to important entrepreneurial sub-groups, such as minorities, women and veterans.

In addition, background material for all of the 2,100 delegates meeting here for five days highlights Carter's accomplishments for those groups in 12 specific discussion areas.

It will not be clear, however, until long after the conference ends next Thursday what concrete changes will result. Action by the president or Congress on the delegate's suggestions could wait until after the election.

"The worth of this momentous conference cannot be gauged for months and years to come," said the Smaller Business Association of New England, Inc. in its January newsletter. "Will the President correct through legislation and many biases against small enterprise that conference delegates attempted to redress? Will the activism generated by the conference of thousands of small business executives be enduring?"

Holding a conference at all for small business people, long a part of the nation's silent majority, is a tribute to their growing influence. For example, many big businesses now want to get involved in the conference, said Arthur Levitt Jr. chairman of the American Stock Exchange board of governors and the conference commission chairman. But Levitt added, at a breakfast meeting yesterday, that the conference is not meant to rubber-stamp the administration or big business wishes.

"Small business has the potential to be the most potent lobby in the history of our country," Levitt said.

"The Proposition 13 movement will seeem pale in comparison to this," Levitt continued. "I sense a mood within the small business community that has been moving from extreme frustration to extreme motivation."

The conference will be kicked off Sunday with an address by President Carter. That will be followed by four days of discussion on 12 topics. The topics are: capital formation and retention, minority business development programs, women in business, government regulations and paperwork, inflation, international trade, federal procurement, energy, innovation and technology, education, training and assistance, and veterans in business.