Bexar County officials moved forward Tuesday with a plan to mail county residents voter-registration forms, defying Attorney General Ken Paxton’s threat to use “all available legal means” to quash the effort.Paxton followed through Wednesday morning, filing a lawsuit in a state district court in Bexar County that seeks an emergency order to block the program. The lawsuit contends that counties lack the authority to send out unsolicited registration applications, while also arguing that Bexar County officials erred by awarding the contract without going through a competitive bidding process.The legal clash escalates a brewing fight between Texas Republicans and some of the state’s largest counties over initiatives to proactively send registration applications to people who are eligible but unregistered to vote. Harris County leaders are weighing…