George Mair, House Speaker Jim Wright's new chief press officer, has dodged the bullet.

Mair, who congressional sources said last month would resign after embarrassing Wright with a series of intemperate letters to newspaper executives, is staying on after all. Hired in December, Mair will complete his six-month, $30,000 contract, according to the speaker's chief of staff.

A former newspaper editor, Mair caused Wright some anxious moments last month when his vivid, frequently misspelled letters complaining about press treatment of the speaker came to light. In a letter to The Wall Street Journal, for example, Mair criticized an evaluation of Wright's first year as speaker as "sly-wink inneundo" and "irrational writing" with "broad and scrullious allegations."

The speaker later apologized to some of the reporters whose work had been criticized by Mair, and House sources said that the press officer's days were numbered.

But Mair proved more resilient than expected, and is now busy arranging meetings between his boss and newspaper editorial boards, doing research and writing, and trying to make sure, in a more low-key manner, that news articles about Wright are more friendly to the speaker.No Talking . . .

At the Defense Department's Military Traffic Management Command, it seems a sure bet that they're not used to making news. Just before this page published a report Feb. 5 on poorly maintained rail tank cars used to transport tons of hazardous substances across the country, Col. G.H. Turner, the command's director of inland traffic, sent this note to "All Employees -- Rail Fleet Division":

"EFFECTIVELY IMMEDIATELY, should anyone receive an inquiry from a reporter with The Washington Post, the director's office will be notified. No information is to be provided. All inquiries will be made known to the Public Affairs Office . . . . " Back in the Senate . . .

Campaign finance reform is back in front of the Senate, complete with threats of a filibuster. The bill, known as S.2., would limit contributions from political action committees and provide for public financing to Senate candidates who agree to spending limits.

Minority Whip Alan K. Simpson (R-Wyo.), trying to cut through the fine points of debate last week, observed:

"If we want to get down right to the nub of it -- and I like to do that with my friend the majority leader {Sen. Robert C. Byrd (D-W.Va.)} and he does that with me -- if this bill passed in its present form, there will never be another Republican majority in the Senate for 40 years. Now that is a good reason for us to hang on by our thumbs.

"So forget all the romance of what it is and {Common Cause chairman} Arch Cox and the national ads. The issue is the Republican Party, this side of the aisle, will not achieve a majority in this body for 40 years. Well, we tasted a little of that majority. We loved it. It was a rich wine. We would like to do it again sometime . . . but we will never have it under S.2." Stepping Up . . .

President Reagan will nominate Federal Highway Administration Deputy Administrator Robert E. Farris to head the agency, the White House announced. If confirmed by the Senate, Farris, 59, will succeed departing chief Ray A. Barnhart.

The president has also named C. Paul Robinson, a longtime official at the Los Alamos National Laboratory, as head of the U.S. negotiating team for talks with the Soviet Union on a nuclear testing agreement. The White House said Robinson would succeed Robert B. Barker, who has returned to his position as assistant secretary of defense for atomic energy.

Sydney Olson has been approved by the Senate Finance Committee for the post of assistant secretary of Health and Human Services for human development services. In her jurisdiction will be Head Start, a variety of programs on the aging and several programs on children and the family. She is a former staff member at the Senate Finance Committee. Historian-in-Residence . . .

The National Endowment for the Humanities has set up its first historian-in-residence program with an emphasis on the teaching profession. Paul Gagnon, chairman of the University of Massachusetts history department, has been selected for the post. He will assist teachers as part of a American Federation of Teachers' program on democratic values.