Her brilliant career. Herald columnist Tom Keane today makes two points about Suffolk County sheriff Andrea Cabral's switch from independent to Republican and, now, to Democrat. I think he's wrong on one, but he's surely right on the other.

1. Keane notes that, last fall, Cabral promised then-governor Jane Swift that she would seek election in 2004 as a Republican if Swift appointed her to fill the vacancy. Keane flatly asserts that Cabral "broke her word" by becoming a Democrat, adding that "in politics, it seems, promises often carry little weight -- which may explain why so many voters are cynical about politicians."

Keane's take is accurate but facile. He goes on to detail how Cabral was disrespected by Governor Mitt Romney. As Swift herself knows, Romney's preferred mode for female officials is to walk 10 feet behind him with their mouths shut, à la Lieutenant Governor Kerry Healey. Okay, Cabral broke her word, but how much was she supposed to take?

And how about that dime-drop re her unpaid student loans that occurred approximately three nanoseconds after she was photographed whooping it up with Ted Kennedy? If she had doubted her party-switching decision at all, she certainly knew then that she'd done the right thing.

2. Keane argues that Cabral might well have lost the election by switching parties. This is counterintuitive -- other analysts have mainly focused on the fact that Suffolk County is overwhelmingly Democratic -- but here, I think, Keane gets it just right.

Cabral, Keane observes, will almost certainly face a challenge in the Democratic primary from Boston city councilor Steve Murphy. Keane writes:

Primary races are low-turnout events, dominated in Boston by more conservative voters, where a candidate's ability to get supporters to the polls is decisive. Murphy has (next to Mayor Tom Menino) the city's most powerful organization, well honed and capable of delivering. Cabral, a political neophyte, has none.

By this calculus, Keane adds, Cabral would actually have a far better chance in the November 2004 general election -- a presidential election, when turnout will be high, attracting the liberal voters whom Cabral needs to win.

This was how former Republican sheriff Ralph Martin did it. It's how Cabral might have done it as well. Instead, perhaps without realizing it, she's chosen a much tougher route.