CARTER AND BAYH FAVORED IN IOWA
Jimmy Carter and Birch Bayh appear to hold lead on eve of Iowa's Dem precinct caucuses to select delegates to Dem natl conv; caucuses, first test of strength of '76 campaign, are expected to attract no more than 10% of state's regis Dems; no deep cleavages have appeared between Dem aspirants; Carter has been campaigning in pol sophisticated Iowa since Feb '75; Bayh has capitalized on network of trade union supporters, closing gap between him and Carter; victory for Carter could prove hollow, since canvassers have found as many as 60% of Dems are still undecided; Bayh illus (L)
