Martha Pennino, vice chairman of the Fairfax County Board of Supervisors, said yesterday she will decide within two weeks whether to challenge former state Del. Ira Lechner of Arlington for the Democratic congressional nomination to oppose 10th District Rep. Frank Wolf (R-Va.).

The sponsor, Del. Dorothy McDiarmid (D-Fairfax) is recovering from pneumonia in her room at Richmond's John Marshall Hotel. How long the measure will be delayed is not known.

For backers of ERA, that's the bad news. The good news is that House Speaker A. L. Philpott (D-Bassett), an ERA opponent, rejected suggestions from other opponents that advantage should be taken of McDiarmid's absence to kill the bill.

"I'll take the heat on this," Philpott said. "She McDiarmid should just rest up and get better."

ERA supporters meanwhile got an unexpected boost when Del. Mary Sue Terry (D-Patrick), previously considered undecided, came out in favor of ERA. She said a survey showed her constituents in the three-county district she shares with Speaker Philpott "favor the . . . amendment by a comfortable margin."

The amendment, which would ban discrimination on the basis of sex, has been approved by 35 of the needed 38 state legislatures. It is scheduled to die next summer unless three more states approve. The Virginia legislature has rejected it for nine straight years.