Rio de Janeiro, September 24 (Xinhua-RHC) -- Brazilian President Dilma Rousseff has widened her lead over main rival Marina Silva in the run-up to the October presidential elections, the latest poll showed Tuesday.

According to the MDA Institute poll commissioned by the National Industry Confederation, Rousseff of the Workers' Party, garnered 36 percent vote, down from 38 percent in the previous poll.

The support of Silva, representing the Brazilian Socialist Party, fell from 33.5 percent to 27.4, while that of Brazilian Social Democratic Party candidate Aecio Neves rose from 14.7 percent to 17.6.

The results show a clear reversal in the initial explosion of support for Silva, who entered the race in mid-August after her running mate, presidential candidate Eduardo Campos, died in a plane crash.

Some political observers had chalked up the early growing support for Silva to the novelty of her candidacy and public sympathy for Campos' death, both of which may now be wearing off.

No candidate is expected to secure more than 50 percent of the votes in the first round on October 5th, and a runoff is likely to take place on October 26th.

In that case, the poll showed Rousseff and Silva remained technically tied, but for the first time in weeks, Rousseff took the lead with 42 percent to 41.

Rousseff is expected to beat Neves with 45.5 percent to 36.5 in a runoff, according to the poll.

The MDA poll surveyed 2,002 people in 137 towns across Brazil on September 20th and 21st. The margin of error is 2.2 percentage points.