When William Jennings Bryan rose at the 1896 Democratic convention in Chicago to deliver what would become one of the most famous speeches in U.S. history, he was not even a candidate for president, much less a leading figure in the party.

The 36-year-old junior congressman from Nebraska stepped to the podium to voice support for a controversial resolution advocating the free coinage of silver.

But his speech -- in which he proclaimed ``You shall not press down upon the brow of labor this crown of thorns, you shall not crucify mankind upon a cross of gold!'' -- so electrified delegates that they swept him to the nomination.Democrats convene in Boston on Monday. But political conventions were not always the scripted, made-for-television productions that they are now.

Before presidential nominees were chosen by voters in state primaries, conventions were raucous, dramatic events where key decisions were often made in smoke-filled rooms by a clique of party leaders, said Allan Lichtman, a presidential historian at American University in Washington.

Amid fiery debates, White House hopefuls maneuvered -- often through dozens of rounds of balloting -- to get the support of delegates, who were mostly chosen by political bosses.

But not since the 1976 Republican gathering in Kansas City -- which pitted incumbent President Gerald Ford against former California Gov. Ronald Reagan -- have candidates fought for the nomination on the convention floor.

While modern conventions keep party infighting hidden from public view, past nominees have been crippled by chaotic conventions that exacerbated divisions within the party.

The 1968 Democratic gathering in Chicago was marked by sharp disagreements over civil rights and the Vietnam War.

As protesters battled with Chicago police outside, delegates narrowly voted down an antiwar resolution and nominated Hubert Humphrey, a favorite of party insiders who considered him more of a hawk.

The mayhem inside and outside the convention was televised nationally.

``Chicago is the horror show people point to of a convention that spun out of control,'' said Cal Jillson, a professor at Southern Methodist University. ``It suggested to middle class Americans that Democrats were ineffectual and caught up in a social revolution.''

More recently, the 1992 Republican convention in Houston, which prominently featured conservatives such as Pat Buchanan and Christian televangelist Pat Robertson, may have hurt the then-President George Bush among moderates.

Buchanan's prime-time address, in which he emphasized opposition to abortion and gay rights and declared ``there is a religious war going on in our country,'' was too strident for mainstream voters, Jillson said.

In 1860, the Democratic Party was so deeply divided over slavery that it held two conventions.

The first, in Charleston, South Carolina, adjourned without a nominee. Delegates reconvened in Baltimore and nominated Stephen Douglas of Illinois, prompting southerners to storm out and nominate their own candidate.

With the Democratic vote split, Republican Abraham Lincoln won....