A small-town girl with no consuming passion for politics, Laura Welch Bush, 54, brings to the White House unaffected charm, quiet humor and a confident personal style, PEOPLE reports in its new cover story about the incoming First Lady. Laura Bush likes Van Morrison and salt-rimmed margaritas on the rocks but is also a self-described introvert who, she says, is "interested in politics because my husband is involved in politics." Distanced skeptics wonder if her traditional 1950s persona might be a bit calculated, but Houston Chronicle columnist Julie Mason tells the magazine: "People who dismiss Laura Bush as a mousy librarian are missing her key role. She's the iron rod at her husband's back. She keeps him from going too far off the deep end when he gets all caught up in his cock-of-the-walk behavior." True, the woman who calls President-elect George W. Bush, 54, "Bushie" in private was overheard telling him to "rein it in, Bubba," when he took to pontificating on the campaign trail. But she tends to deliver her barbs with a wry smile. "She has a dry sense of humor, sly, not a knee-slapper," says a friend. "We were laughing about the downside of running for President, and she decided that she could probably survive it if 'John Goodman doesn't play me' " on "Saturday Night Live." Goodman, it might be recalled, played Linda Tripp on the comedy show.