WASHINGTON — Harry Reid began Election Day with 50 sit-ups and 80 push-ups (very red state of him) and 40 minutes of yoga (very blue state of him).

He spent most of the momentous day in his Senate office, waiting. Just after 2 p.m., Reid, a Nevada Democrat, finally heard some actual news: Britney Spears was filing for divorce.

"Britney Spears," Reid said, shaking his head. "She loses a little weight, and now she's getting all cocky about things." He added, "Britney has gotten her mojo back."

Few would peg Reid, 66, as someone with anything to say about Britney Spears or, for that matter, someone who would ever use the word "mojo." But he is a tricky figure to pigeonhole or predict, a Mormon who opposes abortion and looks more like a civics teacher than someone set to become the most powerful person in the Senate.

He makes an unlikely front man, a role that was displayed Thursday amid chants of "Harry, Harry" at a Capitol Hill rally shortly after Sen. George Allen's concession in Virginia ensured that Democrats would gain a majority in the Senate. Reid is low-key, deferential and somewhat sheepish — qualities that make it easy to misread or underestimate him.

"People can say he is a nice guy, but that just totally misses it," said Sen. Hillary Rodham Clinton, D-N.Y. "He's got a spine of steel, and he will go toe-to-toe with anyone."

Harry Mason Reid is the product of the tiny desert town of Searchlight, Nev., whose father, a hard-rock miner, battled alcoholism and depression before killing himself at 58. The future senator hitchhiked 40 miles to attend high school in Henderson, where he became an amateur boxer.

He came to Washington to attend law school, working nights as a Capitol police officer. He was elected to the Nevada State Assembly at 28, served as lieutenant governor and later led the state's Gaming Commission, a job that pitted him against organized crime figures. (Reid's wife, Landra, once found a bomb under the hood of the family car.) He was elected to the House in 1982 and moved to the Senate four years later.

Reid has brought his pugilistic sensibility to his career, often taking jabs at those he deems unworthy. During Reid's two-year run as minority leader, he called Alan Greenspan, the former Federal Reserve chairman, "a political hack," Supreme Court Justice Clarence Thomas "an embarrassment" and President Bush a "loser" and a "liar." Within that litany, Reid says he regrets only calling Bush a "loser."

All of which has made Reid a reliable bogeyman among Republicans on the stump. But he has also enjoyed the loyalty and, for the most part, unity of a potentially fractious Democratic caucus that includes several prospective presidential candidates.