A new public opinion poll indicates that support for Mexican presidential candidate Andres Manuel Lopez Obrador is slipping, with elections set for July.

The poll, published Monday by the Mexican newspaper El Universal says Lopez Obrador's support among likely voters dropped four percentage points to 38 percent from a month ago.  The former Mexico City mayor represents the Democratic Revolution Party (PRD).

The survey said Felipe Calderon, of President Vicente Fox's National Action Party (PAN) had 34 percent of voter support, up from 32 percent.  Roberto Madrazo of the Institutional Revolutionary Party (PRI) saw his support among voters climb one percentage point to 25 percent.

Voters go to the polls July 2 to choose members of Congress and a successor to President Fox, who by law cannot seek a second term.

Some information for this report was provided by AP and Reuters.