WASHINGTON — Democratic Sen. Ben Ray Luján of New Mexico returned to Congress on Thursday for the first time since he had a stroke, which kept him away from Washington for weeks and temporarily weakened Democrat’s hold on power in the equally divided Senate. In a 50-50 Senate, Luján’s vote could prove critical if Democrats have to confirm Supreme Court nominee Kentanji Brown Jackson without the help of Republicans.Luján received a standing ovation as he entered a morning hearing of the Senate Commerce, Science and …