A few more Democrats in Congress have been named as likely to follow the two recent defectors to the GOP. But a greater threat to the Democratic Party may come from those remaining in it. They are the ones, including some in high office, who would stand back and anticipate voter disenchantment with Reaganomics rather than press toward fresh Democratic alternatives.
Fortunately for America's two-party politics, a number of Democrats are ready to move ahead under the loyal opposition's responsibility to contribute ideas and issues to the public debate. The first wave has come via a new research organization chaired by Duke University president Terry Sanford and listing such other solid Democratic names as Cyrus Vance, Michael Blumenthal, Barbara Jordan, and Edmund Muskie.
Among the ideas is one to hold down inflation that was almost simultaneously lofted by Roy Jenkins of Britain's new Social Democratic Party, whose alliance with the Liberals won a parliamentary by-election last week in a district where the Conservatives had been entrenched. The British version of the proposal would impose an extra tax on employers who exceed wage-rise guidelines agreed to by government, industry, and labor. The American version would go further and penalize companies for exceeding price as well as wage guidelines.
Not that the basic idea is brand new or would tip the political balance on either side of the water. But it exemplifies a willingness to go out on a limb and risk examination instead of simply waiting for the other side's limb to be cut off.
And not that the idea in America came as an official Democratic Party proposal. It was an economist's suggestion circulated by the Sanford group, which notes that its name, Center for Democratic Policy, refers to ''democratic'' in a generic sense. Among other alternatives:
* Break the wage-price momentum through temporary wage-and-price controls. These would be intended to ease the cost of fiscal and monetary restraints on economic demand by reducing their magnitude and duration and thus their negative impact on employment and capital investment.
* Moderate wages and prices by separating a percentage of pay from collective bargaining and making it directly responsive to business conditions and company performance. It could be geared to a formula involving profits, volume of output , a profit-to-sales ratio, or some other relevant indicator.
* Promote saving and capital formation by converting the income tax to an equally progressive personal consumption tax. The Reagan tax cut tilts toward the affluent on the assumption they will benefit the economy through saving, but it gives the same break to the affluent consumer as the affluent saver. The consumption (or expenditure) tax would make saving and investment deductible and thus let the high saver at any income level always pay less tax than the low saver at the same level.
Next month the policy center will follow the topic of inflation with papers on productivity; in December, tax and fiscal policy; later, foreign policy, domestic policy, and governmental and political processes. Here should be grist for the presidential candidates and officeholders who are excluded from membership in the center. It should also help the party's recently formed Democratic National Strategy Council, which does not expect to be ready to adopt policy alternatives until the spring or summer of next year.
Perhaps the party does need that long to pull itself together, interpret the Reagan mandate, and start talking coherently after being dropped to the mat by the GOP. At the same time there may be a temptation simply to put off initiatives and see if the recent poll trends continue. For example, in the congressional race the Republicans are still unusually strong but have fallen farther behind the Democrats than in June. Public approval of President Reagan's handling of the economy has gone below 50 percent for the first time, and his handling of unemployment has reached a low of one-third in a steady decline since the spring.
But it would be shortsighted for the Democrats to delay unnecessarily in letting the public know specifically how they would do better than their opponents. This point was evidently seen by some at the strategy council's first meeting this month - as a matter not only of public responsibility but of political wisdom. What if the Reagan policies look as if they are succeeding right about election time next year? It won't be enough for the Democrats to have done nothing before then but to count on these policies' failure.