On July 30 ABC News President David Westin delivered a response to critics who disparaged the three major U.S. networks for their coverage of the Democratic National Convention, which had just ended. ABC, CBS and NBC aired the convention for just one hour on three of the four nights that it was held. The networks will do the same for the upcoming Republican National Convention.

I applaud Westin for laying out the case for his network's decision in his Post op-ed column, "Don't Blame the Networks." His case was based on new technology. He said that ABC would provide gavel-to-gavel coverage, but in different ways -- using digital television, digital cable and the Internet.

On Aug. 3 The Post published letters from several angry readers (others wrote to me, as well) making the point, as one put it, that it is "appalling that the major networks decided for the public what was newsworthy and what was not during this, possibly the most important presidential election in modern history." Others pointed out that not everyone gets or can afford cable and digital hookups that "come to our homes through privately owned telecommunications lines." The networks use publicly owned broadcast spectrum, a reader wrote, and used to be required to carry public service programming in exchange for use of the airwaves.

I'm very much with the readers on this one. I watched the convention while on vacation. I'm grateful for the substantial coverage by the CNN and MSNBC cable networks, Pub- lic Broadcasting's Jim Lehrer and C-SPAN. Post media reporter Howard Kurtz wrote that ratings for the cable news channels, including Fox, more than doubled from those of four years ago. Public television was up 23 percent. But the three main cable news channels reach only 5 million to 6 million viewers combined, while the three major commercial networks reach tens of millions.

The big networks carried the main events -- the prime-time speeches of former president Bill Clinton and the candidates, Sens. John F. Kerry and John Edwards. And it may well be that the audience, and ratings, would have sunk, along with advertising revenue, if more coverage had replaced other commercial programming.

Nevertheless, the Democrats' convention seemed more interesting and important than just those three speeches. As I watched, I was aware that relatively few people were seeing it, even though it was one of the rare times when there is a chance that a lot of people might be focused on the broad issues of national politics. What also kept going through my head was that the failure to cover this in a more comprehensive way by the only really big, national, high-impact media we have -- namely the big three TV networks -- fit into the pattern of a nation that, in my view, was poorly served and informed before the war in Iraq.

Among the many things not covered by these networks in that hour a night was the speech of former vice president Al Gore, who got a lot of votes four years ago; the criticism by former president Jimmy Carter about the decision to go to war in Iraq; the views of a group of retired military leaders; the emotional, unscripted challenges of the Rev. Al Sharpton (lack of coverage of Sharpton in The Post also drew some angry calls to me); and the convention-rousing keynote address and national debut of a state senator from Illinois, Barack Obama, who seems likely to become the U.S. senator from that state and the Senate's only African American.

The point here is not that there was hard news in these appearances. Rather, they all offered challenges to both the administration and our own thinking on a large array of issues at a time when many people are paying attention and when Republicans and Democrats agree about how crucial this election is. The Republicans will also present a diverse group of speakers at their convention later this month, and that broader aspect of Republican politics won't be on display, in the same way that the Democrats were not covered more thoroughly.

On Tuesday night, when there was no prime-time coverage at all by the three main networks, one reader, watching on C-SPAN, wrote to me after watching Obama, Sen. Ted Kennedy, Teresa Heinz Kerry and others, and called this failure by the networks "a clear dereliction of duty in their responsibility to the American people."

I can understand not televising all of this speech-making. But certainly more of it was more important than what many millions of people were able to see.

Last year, the country entered a war in which the central certainties that the administration offered to the public as explanations turned out not to be the case. Whether or not you believe that going to war was the right thing to do, the performance of the media and Congress in challenging these certainties beforehand left much to be desired.

This year there is a crucial election. It's up to the voters to express themselves about the politicians, but the media -- in this case, the big television networks with their coverage of the national conventions -- should have been more diligent about allowing opposing parties to present their cases more fully to the public when the stakes are as high as they've been in recent years and when there is a decent chance that lots of people are paying attention.

Michael Getler can be reached by phone at 202-334-7582 or by e-mail at ombudsman@washpost.com.