What I like about Plutarch is that he's honest about the flaws these eminent men have, in this case Demosthenes:
The oration which Apollodorus made use of, and by it carried the cause against Timotheus, the general, in an action of debt, it is said was written for him by Demosthenes; as also those against Phormion and Stephanus, in which latter case he was thought to have acted dishonorably, for the speech which Phormion used against Apollodorus was also of his making; he, as it were, having simply furnished two adversaries out of the same shop with weapons to wound one another.A total pro. These days he'd get his own column in the Times.
One may associate Demosthenes with the pebbles he put in his mouth to help him enunciate, but there's also another tale which I liked even better:
Hereupon he built himself a place to study in under ground, (which was still remaining in our time), and hither he would come constantly every day to form his action, and to exercise his voice; and here he would continue, oftentimes without intermission, two or three months together, shaving one half of his head, that so for shame he might not go abroad, though he desired it ever so much.He shaved half his head. That's intense. In some ways he reminds me of Nixon -- an unnatural politician who, nevertheless, succeeds because he wants it so much. And he's willing to go negative with the best of them:
It was evident, even in time of peace, what course Demosthenes would steer in the commonwealth; for whatever was done by the Macedonian [Philip of Macedon, Alex's father], he criticized and found fault with, and upon all occasions was stirring up the people of Athens, and inflaming them against him. ...So that, when the others commended Philip for his able speaking, his beautiful person, nay, and also for his good companionship in drinking, Demosthenes could not refrain from cavilling at these praises; the first, he said, was a quality which might well enough become a rhetorician, the second a woman, and the last was only the property of a sponge; no one of them was the proper commendation of a prince.In the event, the Athenians were overcome by Philip, so maybe Demosthenes should have been more accomodating; but then he wouldn't have been as famous. Although a guy with half his head shaven off is at least notorious.