The study, taken by the MDA firm, gives Rousseff 40.6 percent of voter preference in Sunday's election, while Neves comes in at 24 percent and environmentalist Marina Silva takes 21.4 percent.
This is the first poll in more than a month that leaves Silva, of the Brazilian Socialist Party, or PSB, out of an eventual runoff, and who, after beating even Rousseff in the polls at one point, began to lose support as the race headed down to the wire.
In the MDA survey published Monday, voter preference for Rousseff remained stable, while backing for Neves rose 4 percent as support for Silva dropped 3 points.
In case of a runoff, required if on Sunday none of the candidates wins at least 50 percent of the vote, Rousseff is set to defeat either Silva or Neves.
In the first possibility, the current president will be re-elected with 47.6 percent against the 37.9 percent obtained by the environmentalist.
If the runoff is against Neves, Rousseff would win with 46 percent of the vote, while the Social Democratic candidate would have the support of 40.8 percent of the electorate.
MDA places the margin of error at plus or minus 2.2 percent for the survey taken Thursday and Friday from a sample of 2,002 voters nationwide.