When things are going badly in communist China, the leadership responds by sending some of the intelligentsia out to the countryside for heavy labor. Yesterday, the Kennedy-for-president committee took a leaf from that book.

At a press conference here, Sen. Edward M. Kennedy's brother-in-law and campaign manager, Stephen Smith announced that the struggling campaign will dispatch several of its top Washington-based officials to Illinois and New York, the next two states where Kennedy will mount major primary challenges to President Carter.

Smith also said the campaign will gamble nearly $300,000 -- a considerable portion of its available funds -- on three national half-hour television commercials designed to focus attention on Kennedy's best issue, the economy. He said that the three major networks have not yet said whether they will make the time available.

He indicated that Kennedy will effectively cede the field to Carter in primaries 10 days from now in Georgia, Alabama, and Florida. He said the Kennedy campaign would purchase some media ads in Florida, but none in the other two states, and the best he could say about prospects there was that Kennedy would win "some delegates" in Florida.

The three southern primaries will choose a total of 208 delegates to the Democratic National Convention.

Smith also announced that former Wisconsin governor Patrick Lucey will serve as the Washington-based spokesman for the campaign -- filling a role like that played by Carter's campaign chairman, Robert Strauss.

The Carter campaign has used Strauss regularly to take pokes at Kennedy. Kennedy has had no one performing the same job. But Lucey, who has good contacts with many senior political reporters, now will fill the gap.

A spokesman also indicated that campaign officials will try to go back to regular paychecks for some campaign employes, most of whom have worked for little or no pay for the past month. But salaries will be smaller, and the number of paid employes will be cut in half from the 200 who were on the payroll before Kennedy's big loss in the Iowa caucuses in January.

The new positions announced yesterday include the assignment of Carl Wagner and Paul Tully, two top political organizers, to run Kennedy's campaign in Illinois. Tom Southwick, the campaign press secretary, who previously has accompanied Kennedy on most trips, also will be assigned full-time to Illinois, as will interest-group coordinators Ron Brown and John Howes.

Richard Drayne, who was Kennedy's press secretary through most of the 1970s, will take over the campaign's press operation in New York. Joseph Crangle, a longtime Kennedy supporter who is the Erie County (Buffalo) N.Y. Democratic chairman, will move in the other direction, coming to Washington to woo party leaders around the country.

Paul Kirk, the Washington lawyer who is the top political adviser in the campaign, will begin traveling with Kennedy all the time, Smith said, as will Eddie Martin, who is about the oldest Kennedy hand in the campaign, having started working for the candidate during his first Senate race in 1962.

Smith said that he himself will be working on fund-raising in Illinois and New York during the next few weeks.