If the National Democratic Policy Committee gives you a call and invites you to lunch, don't expect to sit down with Robert Strauss or some other party regular. The NDPC is the latest political arm of Lyndon LaRouche, the many-armed, obscure but bizarre political figure who now wants to be of assistance to Democrats stunned by the last election.

"People who strayed away [from the Democratic Party] will be brought back," vowed LaRouche during a visit to Washington earlier this month.

He was here -- along with his cadre of bodyguards -- to keep an eye on a meeting of international socialists, to chat with Rep. John Jenrette about financing an Abscam memoir, and to monitor the activities of that conservative group advising the Reaganites, the Heritage Foundation. LaRouche thinks the Heritage Foundation is the "disinformation branch of British intelligence" that is connected in some complex, conspirational way to European banking families who are endangering democracy.

Once the head of the U.S. Labor Party, LaRouche's ideological tenets perplex even those who track political fringe groups. In the last election, LaRouche made a bid to become the Democratic candidate for president. His campaign literature included such revelations as, "Zionist circles funded the founding and continuation of the American Nazi Party." LaRouche received $526,253 in matching federal funds, and his supporters say he's preparing to run again in 1984.

LaRouche says Democrats have told him, "You're a central figure of controversy in the party, and the party needs controversy." On that score, at least, LaRouche is a winner.