Tonight, WGBH News hosts the first of three debates, leading up to the general election in November. Running for the office of Attorney General of Masssachusetts, incumbent Maura Healy (D) meets challenger Jay McMahon (R). Jim Braude and Margery Eagan moderate these special presentations. See it on Greater Boston, tonight at 7pm on WGBH 2 and wgbh.org and listen on 89.7 WGBH.