Rep. Cathy McMorris Rodgers took on the medical device tax issue at the Republican House press conference last week. She wore a silk blazer: http://youtu.be/Q4Qfp_XX0uw
The color, fabric and style of this jacket ensure that there's no risk of confusing it with something a man would wear. But this is still a look of clear strength. Here's why: it's fitted, but not tight, and the whole look is streamlined, with no accessories or jewelry and a very carefully coiffed hairstyle.