ROCKVILLE - For months, candidates in the 8th Congressional District in Montgomery County have been amassing campaign money, with spectacular results.

Together, the three principal Democrats and Republican Rep. Constance A. Morella, who is unopposed in the Sept. 10 primary, have collected $5.7 million - more than in any other House race in the nation.

But now comes the critical next phase: translating all of that voluminous cash, enough to buy a fleet of 30 Porsche 911 automobiles, into a spate of television ads.

Within the next few weeks, campaign spots will begin pelting the district's voters like raindrops in a summer storm. With so much money in play, it's likely to be one of the heaviest media deluges in county election history. With the help of their Washington-based media consultants, Democratic candidates Ira Shapiro, Mark K. Shriver and Christopher Van Hollen Jr. are trying to craft ads with a tone and message that will resonate with the suburban district's voters.

A week ago, Democratic congressional leaders urged their District 8 candidates to "refrain from engaging in any kind of negative attacks" that could benefit Morella in the general election by leaving the Democratic survivor's image in tatters.

But the heated campaign climate and high stakes - Democrats consider this a swing seat in their bid to seize control of the House - portend a broadcast campaign that will be anything but mild.

"Are you going to see differences drawn? That's what candidates do," said Peter Fenn, Shapiro's media consultant, whose clients have included former Sen. Paul Simon, an Illinois Democrat, and former Democratic Rep. Geraldine A. Ferraro of New York.

Looking ahead to the general election, Morella, an eight-term incumbent, is already on the air with an introductory ad recounting the story of how she had three children and, when her sister died of cancer, raised six more.

In typical campaign gamesmanship, the Democrats won't reveal when their flood of ads will appear. Such a disclosure could tip their strategy - whether they might seek to break from the pack with an early offensive, or hoard money until the crucial final two weeks. But sources say Shapiro, a former Clinton administration trade negotiator, has reserved TV time around the nightly news hours in the final days before the primary - a move designed to lock in favorable rates and time slots.

In a single pivotal week, a candidate might end up spending more than $400,000 on TV advertising in Washington's expensive market - enough for a typical viewer to see an ad 10 times. While that might sound like saturation to some, "that's where a campaign wants to be in the last week," said Steve Jost, campaign manager for Van Hollen, a state senator. "We'll be competitive. We'll be there," Jost said. He said his campaign was "buying [time] all over the clock" for the primary's final week.

But Shriver, a state delegate whose blue eyes and mass of wavy hair might should serve to remind voters that he is the nephew of former President John F. Kennedy, will probably be even more visible. As of last month's filing deadline, Shriver had $1.7 million in campaign cash on hand, compared with about $800,000 for Van Hollen and $363,000 for Shapiro. A fourth Democrat, Deborah Vollmer, has pledged not to raise more than $5,000.

Kennedy connections

Shriver's campaign is producing television ads with the help of Axelrod & Associates, a political consulting firm that has worked for his cousin, Rep. Patrick Kennedy, a Rhode Island Democrat. Shriver is also reaching out to expected primary voters with laudatory pre-recorded telephone messages from his mother, Eunice Kennedy Shriver, sister of the late president. The Kennedy family has also helped him on his prodigious fund-raising.

"We do have a significant resource advantage in the primary," Shriver campaign manager Mike Henry said. "It gives us more choices."

Among those choices: Shriver can more easily afford to advertise on prime-time shows costing about $30,000 for a 30-second spot. Said Fenn, Shapiro's consultant: "We won't be advertising on Friends. That's not exactly our demographic."

Jost questions whether Shapiro will be able to hang with the others if there is an early media frenzy. While Shapiro is well financed by national standards, his relative lack of money in this expensive race could turn him into an "also ran" before the race nears its end, Jost said.

But Lindsey Marcus, Shapiro's campaign manager, said: "Ira Shapiro will have the funds he needs to win this election. The comments from the Van Hollen campaign demonstrate how nervous they are."

Shriver has focused his criticism more on Morella than on his Democratic rivals. Democrats, needing a net gain of six seats to assume control of the House, consider Morella vulnerable in a district - it also includes part of Prince George's County - that leans Democratic in most elections.

This will be the nation's most expensive campaign in terms of overall money raised, according to the Center for Responsive Politics, a nonpartisan research group that studied the latest Federal Election Commission data.

Although the district has a sophisticated electorate, the candidates know that television will be many voters' introduction to the main primary challengers. "I think the majority are looking out the corner of their eyes but won't really focus until the last few weeks," Jost said. "There is a huge undecided out there."

One reason for the undecideds, according to political consultants, is that the candidates - even Morella, who has a liberal voting record - are alike on most major issues. Their similarities make it all the more important to delineate any differences in issues or experience, Fenn said.

Soft approach or blitz?

But crafting election ads is a tricky business. Like football coaches, the campaigns must decide when to be conservative - focusing on "soft" spots such as Morella's - and when to resort to blitzes criticizing opponents directly or implicitly.

Recently, Van Hollen's campaign was reviewing a half-dozen possible ad narratives with the goal of finding one effectively contrasting his record and experience - as state delegate, state senator and staff member on the U.S. Senate Foreign Relations Committee - with Shriver and his other opponents. "The public believes people's records in the legislature are fair game," Jost said.

He said one ad under consideration mentioned a few opponents by name but did so in the context of discussing credentials for Congress rather than making a personal attack.

While there is a stigma attached to "negative" campaign ads, political experts say going negative often works - and most candidates know it.

The key is to present the attacks in a way that doesn't exaggerate or become personal, said Dave Beattie, Florida-based president of a public opinion and research firm.

"If you talk to people, they say, 'I don't like to hear bad things about everyone.' But when something comes up about someone's record, they'll say, 'Well, I wish I would have known that.' Voters don't mind you talking about contrasts," Beattie said.

But it can go too far.

In the 1996 presidential race, Beattie said, Bill Clinton seemed to exaggerate Republican Bob Dole's voting record on Social Security and Medicare to depict the Republican as not committed to helping senior citizens. "People do expect a level of fairness of accuracy when one candidate talks about another's record," the pollster said.

But voters don't seem to mind conflict. "There is a big audience for Jerry Springer and world wrestling," Beattie said.