MEXICO CITY (Reuters) - Mexican leftist candidate Andres Manuel Lopez Obrador increased his lead ahead of July’s presidential election, while the ruling party’s contender continued his downward trend, according to an opinion poll published in a local newspaper on Wednesday.

FILE PHOTO: Mexican presidential pre-candidate Andres Manuel Lopez Obrador of the National Regeneration Movement (MORENA) greets supporters during a pre-campaign rally in Queretaro, Mexico February 9, 2018. REUTERS/Henry Romero/File Photo

Lopez Obrador, who has run twice for president, led the pack of hopefuls with 27.1 percent in February, according to the survey by pollster Mitofsky published in El Economista newspaper.

The former Mexico City mayor gained 3.5 percentage points over Mitofsky’s January poll, putting him nearly 5 percentage points ahead of his closest rival.

Lopez Obrador has vowed to combat inequality and corruption, but some international investors are concerned over his questioning of the government’s 2013-14 energy legislation, vowing to review recent oil contracts.

Former finance minister Jose Antonio Meade of the ruling Institutional Revolutionary Party (PRI) came in third with 18.0 percent, down from 18.2 percent in January and 19.4 percent in December.

Meade’s campaign has been dogged by a backlash against PRI following a series of corruption scandals and a murder rate that surged last year to a record high.

Ricardo Anaya, former leader of the center-right National Action Party (PAN), ranked second with 22.3 percent, up from 20.4 percent in the prior survey, the poll said. Anaya resigned from the party in December to pursue the presidency in an alliance with the center-left Party of the Democratic Revolution (PRD).

If Meade fails to gain traction, the election could turn into a head-to-head contest between Lopez Obrador and Anaya.

Of 1,000 people surveyed in the poll, 31.4 percent said they believe Lopez Obrador will become Mexico’s next president, up from 25 percent in January. That compared with 23.4 percent who see Meade winning, and 20.7 percent that believe it will be Anaya.

Voters with both the highest and lowest levels of education favored Lopez Obrador, the poll showed.

The survey was conducted Feb. 9-11 and has a margin of error of 3.1 percentage points.