ST. LOUIS (AP) _ A live incumbent found himself locked in a tight race with a dead challenger Tuesday night in a pivotal U.S. Senate election transformed by tragedy during the campaign's final days.

The plane crash that killed Democratic Gov. Mel Carnahan, his son and an aide last month turned the nationally watched contest against Republican Sen. John Ashcroft from notoriously bitter to bizarre.

The crash occurred too late to revise the ballot. No one had ever posthumously won election to the Senate, though voters on at least three occasions sent deceased candidates to the House.

Late Tuesday, with 43 percent of precincts reporting, the race was too close to call. Ashcroft held a lead of 51 percent to 48 percent, but results were out from St. Louis, a Democratic stronghold, and deeply conservative Greene County, Ashcroft's home turf.

``It's probably a little early to start a full-blown celebration,'' Ashcroft told supporters in St. Louis.

Gov. Roger Wilson, who took office after Carnahan's death Oct. 16, said he would appoint Carnahan's 66-year-old widow, Jean, to a two-year term should Ashcroft lose.

Ashcroft, 58, resumed his campaign eight days after the crash, airing his own new TV ad featuring former Sen. John Danforth, a mentor, telling Missourians, ``What's happening today to John Ashcroft is just not right.''

Meanwhile, the late governor's campaign spent $700,000 to broadcast Jean Carnahan making a direct appeal to voters to keep her husband's vision alive.

She answered a dozen questions in writing from The Associated Press, describing views in favor of abortion rights, gun control and other issues, all reflecting stands by her husband in direct opposition to Ashcroft's.

In St. Louis, long lines of voters led a state judge, at Democrats' request, to order the city to keep its polls open until 10 p.m., three extra hours. A shortage of booths, ballots, judges and equipment had vexed the city throughout the day.

But the Board of Election Commissioners appealed swiftly, and a three-judge panel of the Missouri Court of Appeals ordered the polls closed immediately _ after they had been open nearly an extra hour.

The petition was filed by Congressional candidate William Lacy Clay, the Missouri Democratic Committee and the Gore-Lieberman campaign.

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The closeness of the race was reflected in comments from voters on Tuesday. In downtown Kansas City, 59-year-old Richard Cruse voted for Ashcroft. ``It would have been close with Carnahan, but I'm not going to vote for a blind spot with no experience,'' he said.

Ellen Schimpf, 29, voted for Carnahan. ``I'm somebody's wife, and I know I could step in and take over my husband's business if I had to. I think Jean Carnahan could do it, too,'' she said.

Both popular vote-getters elected twice as Missouri governor, Carnahan and Ashcroft were politically like night and day.

Ashcroft, a favorite of religious conservatives when he mulled a White House bid, signed restrictive abortion laws as governor that later were upheld by the U.S. Supreme Court. Carnahan, who served one term as Ashcroft's lieutenant governor and succeeded Ashcroft, vetoed further abortion restrictions as well as concealed weapons legislation.

For years, Missouri political analysts and observers have remarked on the dislike between the two, although Ashcroft and Carnahan both denied it.

Their campaign featured allegations of racism against Ashcroft and a response that included a 40-year-old photo of Carnahan in blackface. They also battled over capital punishment, a controversy generated by Carnahan's decision, at Pope John Paul II's behest, to commute a murderer's death sentence.