In the politics business, there’s a cliché the pros use – “on message.”

A politician is “on message” when what they’re telling you is in compliance with whatever carefully crafted spin his or her handlers have cooked up to enhance their protégé’s political standing. So, when the pol in question makes a mistake, as we humans have a habit of doing once in awhile, it’s crucial for them to remain “on message” lest they compound the damage.

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Yesterday, amid the political fallout from the news that a large light fixture came crashing down onto the Big Dig roadway last month, thankfully and somewhat miraculously not killing anyone, and that this mishap led to the discovery that hundreds of Big Dig light fixtures were at risk of doing the same, Lt. Gov. Tim Murray was on message, telling the Associated Press that it was the right move for the state department of transportation to keep this news from the public for five weeks while they investigated what had happened.

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However, after 24 hours of taking bipartisan heat from key elected officials and the public for being so secretive about an ongoing safety risk, Transportation Secretary Jeff Mulllan went off message, telling reporters he realizes he made a mistake and won’t do it again.

In other words, in this case, as in many others, staying “on message” means staying as far away as possible from the truth and public accountability.

And get this – Mullan claims he never told his boss, Governor Patrick, about this latest incident on the state’s most notorious public project until last Tuesday night, which I don’t believe, leaving us with two possible scenarios – one is, that IS true, and the governor is frighteningly out of the loop on important business under his jurisdiction. Or, two, I’m right to be suspicious, and the administration is being “on message” – the message being, cover the Governor’s rear at all costs.

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You can listen to Keller At Large on WBZ News Radio every weekday at 7:55 a.m. and 12:25 p.m. You can also watch Jon on WBZ-TV News.