BostonGlobe.com Political Headlines - September 15, 2014 September 17, 2014 Here are the top political headlines from BostonGlobe.com today: At a White House rich in coffee lore, no word on president’s preference: It turns out that the Obama White House makes it nearly impossible to find the source of its coffee and how it is prepared. Matt Viser details the story. Many yet to be persuaded in Mass. governor’s race: Choosing the next governor can take a while when the choices are coming out of 2010’s recycling bin. Nestor Ramos reports. Baker, Coakley steer clear of far-reaching tax talk: Gubernatorial candidates Charlie Baker and Martha Coakley are treading cautiously when it comes to the charged issue. Michael Levenson reports. Martha Coakley’s base shows fissures: Coakley has still got to persuade people to vote for her, and the seeds of doubt are visible to anyone willing to look. Adrian Walker details the story.