The "buried importance" some political observers see in today's special election in Philadelphia is not expected to produce more than a trickle of voters for the 3rd Congressional District contest to choose a successor to Democrat Raymond F. Lederer, who resigned from the House last May after his conviction of Abscam charges.

The working-class district is 4-to-1 Democratic in registration, and the tow leading candidates in the four-man field have been Democrats all their lives. But a series of interlocking rivalries has made the race of interest to political insiders in both Washington and Philadelphia.

A close race is expected between the betting favorite, Philadelphia Democratic Chairman David B. Glancey, 36, and state Sen. Joseph F. Smith, 51, who re-registered as an independent and also accepted the Republican nomination after Glancey lined up a majority of the ward leaders for the Democratic nomination.

Old alliances have been shattered and some strange new partnerships formed in the contest. Glancey has the strong backing of Mayor William J. Green III, a Democrat, who once held the same House seat, as did his father before him. Thanks to Green, Glancey has had campaign visits former vice president Mondale and Sens. Edward M. Kennedy (Mass.), Bill Bradley (N.J.), and Joseph R. Biden Jr. (Del.)

But Smith, who has a staunchly pro-labor record in his 11 years in Harrisburg, is backed by the AFL-CIO and most of its major constituent unions and by elements in the city Democratic organization who are loyal to former Mayor Frank Rizzo and on the outs with Green. Smith also is backed by the city Reopublican organization and by neighboring Rep. Charles F. Dougherty (R-Pa.). Despite Dougherty's urgings, the state and national Republican parties have shunned Smith, who echoes Glancey's criticism of the Reagan budget and has pledged to caucus with the Democrats if elected.

Although Glancey has the advantage in both funds and organization, the outcome is regarded as doubtful because the turnout is expected to be light and Smith is well-known through his legislative service.

In Philadelphia, the race is seen as a test of strength for Green, who handpicked Glancey as city chairman and backed him strongly in this race. A loss for Glancey would encourage a challenge to Green's re-election either from Rizzo or from Dougherty.

In Washington, the race is seen as foreshadowing a possible loss for one party or the other in the 1982 congressional election. The 3rd District is likely to be carved up in the redistricting later this year that will cost Philadelphia one of its four House seats. If Glancey wins, he has indicated he would challenge Dougherty next year, but if Smith wins with Dougherty's help, the guessing is he would run against freshman Rep. Thomas M. Foglietta, a Democrat.

The other two candidates in the contest are Charles L. Duncan Jr. of the Consumer Party and David Dorn, a Libertarian.

In previous special elections this year, Republicans have held seats in Michigan and Ohio. Democrats have held a seat in Maryland and taken over a Republican seat in Mississippi.