Congressional Democrats — bolstered by Americans’ worries about the war in Iraq — have opened their largest lead in so-called generic-ballot tests since the summer of 1998, giving party leaders more optimism than they could have imagined having just a few months ago.

But experts differ about how much should be read into such poll results, with some questioning whether such a broad question picks up trends driving voters in the small number of seats that are considered truly competitive.

The generic ballot question — most commonly framed as, “If the election for Congress were being held today, do you think you would vote for the Democratic candidate for Congress in your district or for the Republican candidate?” — has long been a favorite tool of independent and partisan pollsters who want to gauge the electorate’s overall mood.

In most election cycles, generic-ballot results fluctuate between a 5-point lead for either party. (Voters who either say they don’t know or who refuse to answer typically number in the single digits.)

But two polls in recent weeks — one conducted by Time/CNN and the other by The Associated Press/Ipsos — show Congressional Democrats with a 13-point and 9-point generic-ballot lead, respectively. Both gaps are unusually wide for either party.

Democrats were quick to capitalize on the news.

“The results on the generic ballot represent a sweeping repudiation of Republican stewardship,” said Democratic Senatorial Campaign Committee Chairman Jon Corzine (N.J.).

Rep. Robert Matsui (Calif.), Corzine’s counterpart at the Democratic Congressional Campaign Committee, added, “There is a belief among the American public that things aren’t going well. That is not because of the last week but because of the last four months.”

Pollsters, aides and strategists agree that the poll results suggest a climate of dissatisfaction among voters. But these experts parted ways — generally along party lines — on the question of whether that sentiment will translate into Democratic gains in November.

National Republican Congressional Committee Chairman Tom Reynolds (N.Y.) acknowledged that the current generic-ballot split is “a little higher than we are used to seeing it,” but he blamed it on the unusual torrent of negative news coming out of Iraq.

Whatever the reason, Democrats believe that their current lead in the generic-ballot test could foretell a major shift.

Fred Yang, a Democratic pollster who typically handles several House and Senate races each campaign cycle, said a lead of that magnitude “would be predictive of us taking back a wide number of seats.”

A 3-to-5 point lead on the generic ballot would mean that “the wind is at your back, but it is every man or woman for themselves,” Yang said. By contrast, he said, “when you are [up by] 9 to 13 points, you are at wave proportions.”

Political observers are constantly watching for signs of a repeat of 1994, when voter dissatisfaction with Democratic control of Congress and the White House, coupled with a national Republican message of reform, made possible a 52-seat GOP pickup in the House and a nine-seat gain in the Senate.

The experience of 1994 illustrates the dangers of relying too heavily on generic-ballot tests. At this time in 1994, Democrats actually had a 6-point lead in the generic ballot. Even in the final Gallup poll taken before the election, the GOP only had a 7-point edge.

Democratic pollster Alan Secrest warned that past cycles have shown a capacity for major fluctuations in the generic-ballot results as the election draws near.

“If you look at some of the years when we had big changes, you see significant differences on mood-related questions between the first and second quarters [of the year] and the third and fourth quarters,” Secrest said.

In fact, in every Congressional election over the past decade, Democrats held the lead in the generic ballot heading into the summer of an election year. In three of those five elections, they picked up House seats. In only one did they gain Senate seats. (See chart.)

“The generic ballot helps reflect the terrain that individual campaigns are being fought on,” said Glen Bolger, a prominent Republican pollster. “Plenty of Members of both parties have won races with the terrain against them.”

Part of this divergence has to do with structural issues surrounding the question.

Even Democratic pollsters acknowledge that their party has a built-in advantage in generic ballot questions. This is because Democrats — even after a round of redistricting that served to purify more and more seats into one party’s camp or the other — still have more districts heavily weighted in their favor.

Such Democratic strengths, Republicans (and many independent experts) argue, shed little light on how the Democrats will do in more marginal “swing” districts.

Republicans add that there are far fewer competitive races on the board today than there were a decade ago. “If you ended up on election day with a big disparity in the generic ballot, it would have an impact, but the number of seats it would have an impact on is small,” said a senior Republican operative who follows Congressional races closely.

House Democrats entered the 2004 cycle with the stated goal of expanding the playing field, which has shrunk consistently since 1998. The trend was exacerbated by post-2000 redistricting, leaving fewer than two dozen seats truly competitive in 2002.

Matsui and House Minority Leader Nancy Pelosi (Calif.) have touted their efforts to recruit candidates in nontraditional districts like Kansas’ 2nd and Nebraska’s 1st and 2nd districts. DCCC officials argue that they now have 40 serious candidates running in Republican-held seats either as challengers or in open-seat situations.

At a briefing for reporters Friday, House Minority Whip Steny Hoyer (Md.) said that at this point in 1994 Republicans had 60 top-tier candidates with 38 seats needed to win back the House — a ratio of 1.6 candidates to every seat.

Currently, by Hoyer’s estimate, Democrats have 28 top-tier candidates ready to go and have only a 12-seat margin to overcome, giving them a ratio of 2.3 candidates for every seat. That means “that if the wind comes, we are in a much better position than the Republicans were in 1994 to take back the House,” he said.

The NRCC’s Reynolds was blunt about the Democrats’ alleged shortcomings, regardless of the current generic ballot.

“Democrats have failed to raise the money they need, failed to recruit top-tier candidates, and the guy on the top of the ballot isn’t doing them any favors either,” Reynolds said.

Secrest expressed more caution than Hoyer did, but they were still optimistic.

Secrest called it “foolhardy” to predict specific seat gains based on the generic ballot in May, but he added that the positive numbers could have “a very beneficial effect” on fundraising and base enthusiasm.

Erin P. Billings contributed to this report.