The Democratic-backed candidates say they are running, in the words of their bumper stickers, to "Save Metro."

But their Republican-endorsed opponents claim they're the ones who are "working for Metro."

In what some Arlington Democrats call a race between "The Pair that Cares" and "The Pair That's There," support for Metro has become a key issue in the county's Nov. 6 elections.

Democrats Mary Margaret Whipple and Charles Rinker are attempting to unseat incumbent Board Chairman Dorothy T. gRotos and Vice-Chairman Walter L. Frankland Jr. over their commitment to mass transit -- an issue that is being fueled by public anticipation over the Dec. 1 opening of four Arlington subway stations.

At stake is whether Republicans can continue controlling the five-member Arlington County Board for the next three years, enabling them to make vital decisions about Metro funding and housing in the county. Since Arlington is one of the six largest Metro jurisdictions, its positions on the future of the subway can carry veto power.

Last year, for the first time in nearly a decade, Republican-backed independents wrested majority control of the Arlington board from a Democratic coalition, with the election of Stephen H. Detwiler. Detwiler, whose term runs three more years, joined Grotos and Frankland, forming what the three call the "new Republican majority." Board members John W. Purdy and Ellen M. Bozman are endorsed by a Democratic coalition.

This year, with ridership and popular support for the Metro system running high in the Virginia suburbs, opposition to Metro is widely perceived as a political kill of death.

Democrats Rinker, 38, a legislative liaison for ACTION, a federal antipoverty agency, and Whiple, 39, chairman of the County School Board, claim Grotos and Frankland repeatedly have tried to stymie the system since their elections in 1975.

"I have never voted against Metro," counters Frankland, a 53-year-old Washington lobbyist of silver interests. "There has never been a question of Do you favor Metro? Yes or No.'" He says his critics have confused his questioning various schemes for financing the transit system with his support of public transit.

His running mate, Grotos, 48, a housewife with a long record of working for conservation causes and the Republican Party, says voting against Metro is unthinkable. "Even the Pope couldn't stop Metro, it's so popular," she said.

There's no dispute on the Metro stance of a fifth candidate in the race. Michael Maddox, a 32-year-old Energy Department research analyst running with Libertarian Party support, calls Metro a "tax monster" and says he opposes completing it.

Most of the debate on Metro in this fall's campaign centers on Frankland's county board votes on various Metro questions.

According to a large chart the Democrats take with them to most meetings, Frankland opposed:

A financial plan for completing the 101-mile system (October 1978).

Endorsing a regional gasoline tax for Metro thereby removing the burden from the property tax (October 1978).

Funds to complete the four Arlington stations that will soon open along Wilson Boulevard (December 1976).

Grotos, who voted for completing the full 101-mile system, opposed the concept of a regional sales tax as well as funds to complete the four Arlington stations, according to countyboard records.

Grotos and Frankland say their votess have reflected their concern over financing the subway. At candidates' nights and in mailouts they take credit for opening the four stations a month before their scheduled Jan. 1, 1980, date. "Grotos and Frankland," according to one brochure "are keeping it (Metro) going . . . they're on the track!"

Frankland, executive vice-president of the Silver Users Association, and a retired Army lieutenant colonel, says "The media paints me as being anti-Metro."

Grotos said she could not remember voting against the regional tax concept, but added that while she supports shifting the Metro burden from the real estate tax, "I also oppose any new taxation."

Rinker and Whipple charge that their opponents are belated or "born-again" Metro supporters. "Any public official who thinks you cany say you're for something and then not vote for financing it is naive," said Shipple. "And anyone who three years ago could not see the value of Metro is very short-sighted."

Rinker said that "Dorothy and Walter are trying to cover up their votes. I've suggested to them that they should just say they made a mistake and now they're for Metro, but they haven't taken my advice."

While Democrats hope that Grotos and Frankland are vulnerable on their Metro records, one Republican leader said he believed their Metro criticisms might help.

"Sure there are a helluva lot of people who like Metro and who ride it, but they don't want to pay for it," he said. "People in Arlington vote on personalities and pocketbooks."

The incumbents point out that the county board this year cut the personal property tax rate by 20 cents and the real estate tax by 16 cents, "the largest reduction in the history of this country," in Frankland's words.

"I don't think that was a great achievement," Whipple said. "It was an easy thing to do . . . made possible by a very unusual and very large surplus. Anyone who had been on the board this year would have made a large tax cut."

While the candidates may differ on the reason for the tax cuts, all agree that Arlington's dwindling stock of moderate-cost rental housing is another major issue.

More that half of Arlington's 165,000 residents are tenants, and the county currently has the lowest apartment vacancy rate on any jurisdiction in the metropolitan area. This year alone, condominium conversion plans have been unveiled at several of the largest garden apartment complexes, a situation that parallels the District.

Frankland and Grotos say there is little they can do to stop conversions without enabling legislation from the Virginia Assembly. "In the nine months we've been in power we've been completely supportive of tenants," said Grotos, who said she favors strengthening state laws that govern conversions.

Frankland complains that his "new majority" is unfairly being blamed for Arlington's housing problems.

"All of a sudden the Republicans take over in January and there's a housing crisis," Frankland said. "Well, who's been in power for ten years? If (the voters) give us a chance, we'll show (them) how to work with developers."

Rinker, a former president of the nonprofit Arlington Housing Corp., and Whipple say they are not balaming the Republicans for the conversion crunch.

"The board has reacted to the housing cruch only when the public outcry got so great they had to respond," Whipple said, adding that it took five months for the Republicans to appoint a housing advisory committee.

"We don't oppose condominium conversion in and of itself," Whipple said. "The problem is displacement." Rinker added that the tow favor giving developers incentives to maintain rental units in some projects and getting the state to approve a tax-free bonding authority for low-interest loans.

Observers of both parties and the candidatess themselves predict that the race will be close. The turnout of Arlington's 75,000 registered voters is exptect to be particularly low because there are no state or national offices to be decided.

In Arlington, board members are elected at-large, serve four-year terms, and are paid $9,000 for what are considered part-time jobs. Candidates for the board officially run on a nonpartisan basis, although they are backed by partisan groups.

The board is responsible for setting overall guidelines for the county government, as well as enacting local ordinances and taxes.