By Dave Graham

MEXICOCITY (Reuters) – The former political party of Mexican President Andres Manuel Lopez Obrador issued a blistering attack against the veteran leftist on Wednesday, accusing him of pushing the country towards authoritarianism.

In a full-page advertisement in newspaper Reforma, the Party of the Democratic Revolution (PRD) said Lopez Obrador was dismantling 30 years of reforms aimed at checking the power of the state under Mexico’s old rulers.

“We’re in the process of restoring a presidential, centralizing and authoritarian system which weakens and suppresses the legislative branch and undermines the independence of the judiciary,” the PRD said.

Once Mexico’s main left-of-centre group, the PRD has been reduced to a rump of its former self since Lopez Obrador split to form a new party after finishing runner-up in the 2012 presidential election.

Spokespeople for the president and the party he founded after the leaving the PRD, the National Regeneration Movement (MORENA), did not immediately reply to requests for comment.

In office since December, the president has enjoyed soaring levels of popularity while blaming Mexico’s problems on old rivals and the previous six administrations.

He has dominated the political agenda with a daily morning news conference, often using it to criticise many checks and balances on his power from within civil society and the media.

The PRD’s attack on him underlines the increasingly partisan flavour of politics in Mexico under Lopez Obrador.

Lopez Obrador says he is democratizing freedom of expression with his media conferences and has regularly pushed back against suggestions he aims to install an authoritarian government.

Through MORENA and its allies, Lopez Obrador has firm control of Congress, and adversaries fear that his concentration of power could soon extend to the Supreme Court.

MORENA has proposed increasing the number of judges in the court to create an anti-corruption chamber. His supporters reject criticism that the move is aimed at controlling the body.

For most of the past century, Mexico was ruled by the Institutional Revolutionary Party (PRI), which melded patronage and vote-rigging with corruption and authoritarianism.

As disaffection with the party’s rule grew, a group of reform-minded politicians formed the PRD in the late 1980s. Like Lopez Obrador, many of its leaders once belonged to the PRI.

Serving as PRD chairman in the late 1990s, Lopez Obrador went on to become mayor of Mexico City for the party in 2000, and narrowly failed to win the presidency six years later.

Lopez Obrador refused to accept defeat in 2006, saying he had been robbed. Relations between him and other senior PRD figures gradually broke down and he decided to leave the party behind following his 2012 election defeat.

Many former stalwarts of the PRD joined Lopez Obrador after he founded MORENA, and the remnants of the party backed a rival candidate in the 2018 presidential election.

The PRI ruled Mexico from 1929 until it was voted out in 2000. Returning to power from 2012 to 2018, the PRI suffered a record defeat at the hands of Lopez Obrador in July.

(Additional reporting by Ana Isabel Martinez; Editing by David Gregorio)