HARARE, Zimbabwe  President Robert Mugabe’s decades-old control of Zimbabwe seemed to erode further on Tuesday, as diplomats, analysts and opposition members contended that talks were under way for the 84-year-old leader to step down after trailing in Saturday’s election.

Morgan Tsvangirai, the opposition candidate who appears to be ahead in the voting, denied in an evening address that his party had been in discussions over Mr. Mugabe’s resignation, saying he would “not enter into any deal” before the vote results were officially announced.

But his denial was at odds with a flurry of accounts that the two sides were having discussions about a possible transfer of power.

The nation’s election commission has yet to release any results in the presidential race, only a steady trickle of outcomes in contests for Parliament. But a projection by an independent civic group, based on data from polling stations, gives Mr. Tsvangirai a lead of about 49.4 percent to 41.8 percent, raising the prospect of either outright defeat for Mr. Mugabe or a runoff should neither one win a majority.