At my first political convention, Adlai Stevenson unexpectedly left his vice-presidential choice to the delegates. It led to an exciting two-ballot battle but saddled him with a running mate he didn't much like.

In the 1960s and 1970s, I covered three conventions at which uncertainty about the nominee sparked several tense days of maneuvering.

All four nominees — Democrats Stevenson, Hubert Humphrey and George McGovern, and Republican Gerald Ford — lost. Ultimately, leaders of both parties decided certainty was a safer path to victory.

Still, this week's Democratic National Convention in Denver starts with some doubts, mainly regarding how enthusiastically Hillary Clinton's troops will back Barack Obama.

Mostly, however, Obama's Democrats and John McCain's Republicans the week after in St. Paul will display a carefully scripted facade aimed at giving their party its best chance of winning.

That raises the question of whether conventions are still worth the time, effort and money that are spent by the political parties and the nation's news media.

Here's one enthusiastic vote in their favor. It's based on more than nostalgia for what politics was like before television turned raucous convention halls into large TV studios.

The reason: Obama or McCain will be the next president.

However scripted and flawed, the conventions and the upcoming televised debates offer voters the best chance to scrutinize them and their supporting casts.

Voters will see not only how the candidates present themselves and their ideas but get a picture of the two parties' very different personnel, demographics, approaches and views.

The formal speeches may seem simplistic and one-sided. But reporting and analyses of news organizations — from mainstream print and broadcast media to a multiplicity of independent voices — will augment the presentations.

The nation's major television networks again are limiting coverage and will mostly stick with their regular sitcoms and reality shows. They include a new NBC series, "America's Toughest Jobs," which presumably does not include the presidency.

But there will be no shortage of opportunities to read and watch everything from the formal speeches to the interviews and analyses on the 24-hour cable news outlets.

Convention viewing requires a big investment of time. But those who are interested, or undecided, can get a good sense of their options.

The two parties, after all, are markedly different.

The Democratic convention will display greater racial diversity, along with endless speculation on the potential impact of having the nation's first black president.

Its platform and other issue debates may indicate how an Obama administration would deal both with the nation's economic woes and with the fiscal mess that developed during the Bush years.

By contrast, the GOP gathering will confront — or avoid — the question of how much McCain would break with Bush administration policies. It may show whether he would stick to its strategy of slowing any Iraq withdrawal until convinced that ground conditions will ensure political stability.

The GOP convention may demonstrate the degree to which religious conservatives still hold sway, given that some leaders seem unenthusiastic about McCain.

Each party will seek to dispel the notion that it appeals to only a narrow segment.

The Democrats, while maintaining their support of abortion rights, have allotted speaking time to Sen. Bob Casey, an abortion-rights foe whose father was denied a similar spot 16 years ago.

Republicans, though officially against abortion rights, will spotlight two pro-choicers, California Gov. Arnold Schwarzenegger and former New York Mayor Rudy Giuliani. There's even talk of a McCain running mate at odds with the party orthodoxy.

In any case, these four-day extravaganzas will provide viewers with the best sense to date of what Obama or McCain would do if elected.

That may be less entertaining than past floor fights, but it endows what critics call relics with much modern-day value.

Carl P. Leubsdorf is Washington bureau chief of the Dallas Morning News. E-mail him at cleubsdorf@dallasnews.com.