The Label buttons -- two bare feet linked by the name "Ira"--were left over from another campaign four years ago when Ira M. Lechner, Arlington Democrat and Virginia liberal, wore out four pairs of shoes walking 300 miles in a bid for his party's nomination as lieutenant governor.

Lechner lost the nomination in both 1977 and 1981, but yesterday the 47-year-old attorney and a handful of his supporters pinned the buttons on once more, this time to announce Lechner's candidacy for the Northern Virginia congressional seat now held by Republican Frank Wolf.

Lechner is the first Democrat to announce in the 10th District, which includes Arlington and Loudoun counties and the northern half of Fairfax County, since former congressman Joseph L. Fisher, the party's favorite, accepted a job with the administration of Gov.-elect Charles S. Robb on Tuesday.

"Time is very short," said Lechner, speaking from a podium in front of the Virginia Employment Commission in Fairfax County, " . . . which is why we have to hit the ground running."

It was an aggressive start to what promises to be an energetic campaign, in keeping with Lechner's past political performances. After the stop at the Employment Commission, where he decried the area's growing unemployment, Lechner moved on to the Leehigh Apartments in Arlington where he called for a two-year national moratorium on condominium conversion.

"I would like make this congressional seat the focus of new, innovative housing policy," said Lechner, a former Virginia state delegate and a primary author of the state's Tenant Landlord Act of 1974.

At both stops, Lechner pounced on Reagan administration policies, a theme Democrats hope will turn the 10th District against Wolf, a Reagan loyalist, in November.

By moving quickly, Lechner hopes to stymie any challenge from Democrats who fear his brand of old-fashioned liberalism will fail to win back the conservative outer suburbs that helped defeat Fisher in 1980.

Lechner also angered some moderate Democrats last summer when delegates favoring him took over the 10th District Democratic Committee, making it more predominantly liberal. "He has a real problem in that regard," said one Democrat. "Let's face it. Ira is not the best one at mending fences."

Finally, some Fairfax Democrats are eager to nominate their own candidate for Congress, claiming that a well-known nominee from Fairfax could offset the Republicans' edge in the county.

Lechner yesterday asserted that he is "a proven vote-getter in Northern Virginia." He pointed to his race in 1975 when, as the "floater" delegate representing Arlington and Alexandria, he led the Democratic ticket in both jurisdictions. In the 1977 primary, Lechner beat two Democrats, including Robb, in the 10th District, although he lost the race for lieutenant governor statewide. And in 1981, Lechner delegates again swept Northern Virginia in his second unsuccessful try for the second spot on the ticket.

He also said his organization, made up largely of liberal activists and labor leaders, is still in place six months after the state convention. "I hope we'll be unified," said Lechner, "but I don't fear a primary."

So far, the candidates considering a run against Lechner include Arlington County Board Member John Milliken, a former top aide to Fisher; Fairfax County Board Supervisor Martha Pennino, and former Fairfax State Del. Raymond Vickery Jr.

A "stop-Lechner" drive could produce problems for the Democrats who already are feeling the loss of Fisher, a popular candidate who was viewed as able to unite the party's disparate elements.

Lechner's announcement was seen by one of his backers yesterday as a try at a "typical Ira preemptive strike."

"Whoever runs now is going to be seen a 'stop-Ira' candidate, which could be very damaging," said Paul Goldman, a Democratic strategist with strong ties to Lechner, "How else are they going to be able to explain their candidacy?"