MEXICO CITY, Sept 23 (Reuters) - The congress of the Mexican state of Sonora voted on Thursday to legalize same-sex marriage, meaning that about three quarters of the country"s regions have now made the practice legal. Lawmakers in the legislature of Sonora, a large northern state that borders Arizona and New Mexico in the United States, approved the change in the law with 26 votes in favor and seven against. On Wednesday, the central state of Queretaro, long regarded as one of the most conservative in the country, also approved same-sex marriage legislation in what Mexican media reported was the 23rd of 32 regions to do so. The push for marriage equality and LGBT rights has gathered pace since Mexico City became the first region to legalize same-sex marriage in 2009. Leftist President Andres Manuel Lopez Obrador has been at pains not to alienate socially conservative voters, but many activists in his National Regeneration Movement (MORENA) are staunch supporters of socially liberal causes.