In the late 19th century, the Populists - a protest movement of mainly disaffected farmers and workers - threatened to overturn established authority.
Despite all the public hand-wringing about negative advertising, political veterans will tell you that it persists because, more often than not, it works. But tearing down the other guy has another attraction: It can be a substitute for building much of a case for what the mudslinger will do once in office.
Kennedy saw the presidency as the vital center of government, and a president's primary goal as galvanizing commitments to constructive change. He aimed to move the country and the world toward a more peaceful future, not just through legislation but through inspiration.
Whatever the long-term legal prospects for same-sex marriage, President Obama's willingness to put the matter front and center in an election year can at least make him a candidate for inclusion in Kennedy's Profiles in Courage.
Few American presidents are held in higher esteem than Thomas Jefferson. Though historians have scrutinized every phase of his long public career and found him wanting in a number of respects, he holds an unshakable place in the pantheon of American heroes.
By the time a second term rolls around, the illusions about a president have largely evaporated.
Besieged by lawsuits that threatened to engulf almost everyone at the White House, Clinton assistants shunned paper or e-mail records of their daily deliberations. One told me that he would go down the hall to confer with his division chief face to face rather than discuss an issue on the telephone.
Coming out of WWII, there was the assumption, the hope, the vision of a world at peace, of a kind of Wilsonian universalism, that we and the Soviets would get along, we'd have a kind of lovefest for as far into the future as anyone could see.
To be sure, hunters and sportsmen back gun rights. Beyond that, there are millions who see guns as a defense against fear - fear of criminals breaking into their homes or assaulting them on city streets.
As someone who has more than a passing acquaintance with most of the 20th century presidents, I have often thought that their accomplishments have little staying power in shaping popular views of their leadership.
The consequence of the Bay of Pigs failure wasn't an acceptance of Castro and his control of Cuba but, rather, a renewed determination to bring him down by stealth.
If nobody trusts you as president, then you can't get anything done.
Vice President Biden's surprising declaration of unqualified support for gay marriage seems to have forced President Obama into a public endorsement of a controversial social issue. It is difficult not to suspect that Biden's pronouncement aimed to give the president some political cover.
When President Obama first unveiled his gun control proposals recommending a ban on assault weapons and high-capacity magazines and better background checks, there seemed to be momentum behind the effort. But then the proposals ran into a wall.