The Democratic primary race for the 4th District seat in Prince George's County is not nice. In fact, it's downright nasty.

Incumbent Richard Castaldi, 45, and challenger G. Frederick Robinson, 46, have accused each other of being a tool of big developers, a charge that can mobilize voters concerned about rapid growth in the district that takes in a north-central section of the county including Greenbelt and Bowie.

The race also has turned to personal charges. Robinson has complained that Castaldi hired his wife to work as his administrative aide, to which Castaldi replies, "I married my administrative assistant" who came to work for him before they were married.

The race seemingly has pitted against each other the municipalities of Greenbelt, population 17,000 and Castaldi's home, and Bowie, population 41,000, where Robinson serves on the City Council -- although both candidates claim to have supporters across the district.

The race is so divisive that the county's power brokers have left the council seat off their sample ballots that show the candidates they support. State Sen. Leo Green, who is known to dislike Castaldi and reportedly privately supports Robinson, is publicly staying neutral. So are the district's three Democratic state delegates, all of whom are from Bowie.

"We thought it best to let the candidates themselves slug it out," said Del. Mary A. Conroy. "Let the people decide."

The district has 21,714 registered Democrats, 12,813 Republicans, 4,949 independents and 35 Libertarians. First-time candidates John Kellenger, 37, of Bowie, a training education consultant, and Thedore Henderson, 48, of Greenbelt, a county public school counselor, are competing for the underdog Republican nomination. Their race has been a love feast compared with the Democrats, who have waged a battle of endorsements, press releases and rhetoric.

"By any criteria, ethics and personal integrity, it's like night and day as far as I'm concerned," said Robinson, comparing himself with Castaldi.

"The rhetoric has gotten very high, just because Robinson is trying so hard to call attention to himself," said Ann Gordon, the council member's aide, campaign manager and wife. "We're going to back away from that rhetoric . . . . "

But Castaldi and Robinson brandished and crossed rhetorical swords at a candidates forum in Bowie soon after Gordon's statement.

"You were wholesaled by a developer, Mark Vogel, who is the Donald Trump of Prince George's County," Castaldi told Robinson, referring to a $100-a-ticket fund-raiser for Robinson that Vogel sponsored at Bowie Golf and Country Club.

"My opponent ought to switch jobs and work for an S&L," Robinson said, alleging close ties between Castaldi and other developers from whom he received large contributions in past campaigns.

Counters Castaldi: "It's real interesting he would indicate I'm too close to developers when I've introduced more controlled growth legislation than any council member the last eight years."

Robinson, a county police major, has the support of police organizations (including the Greenbelt Fraternal Order of Police Lodge 32), most Bowie politicians and two past presidents of the NAACP.

Bowie Mayor Richard J. Logue said he supports Robinson "150 percent." Greenbelt Mayor Gilbert Weidenfeld, as a federal employee, cannot take a partisan position; his wife, Micki, is Castaldi's Greenbelt coordinator.

On matters of substance, the candidates agree on the proposed eastern bypass: they're both against it. They also agree that busing for school integration is no longer workable or cost-effective in a majority-black county.

The candidates part company particularly on matters affecting Bowie, including access to the county's Sandy Hill landfill on Route 197 and the location of a Bowie-owned sludge treatment plant outside city limits. Castaldi rejected alternative access to the landfill, citing cost.

Castaldi also opposed the city's sludge plant near Upper Marlboro as environmentally undesirable. At the candidates forum, Robinson contended that Castaldi had seen and signed off on the sludge treatment site.

"I don't know where you're getting your information from," Castaldi said at the forum. "It's misinformation, as usual."

In the Republican contest, the decibel level is decidedly lower.

Kellenger said, "There's a lot Henderson and I agree on. It's just a difference in style." Said Henderson, running against one-party rule: "It's important to have a second ear when the debates go on. I feel I could do that better."