Carnahan, 66, was locked in a tight contest with GOP Sen. John Ashcroft at the time of his death, and Democrats nationwide were counting on him to help narrow a GOP Senate majority of 54-46.

"I have ordered my campaign to cease all campaign operations indefinitely," said Ashcroft, a first-term Republican. "Obviously this is not a time for politics, this is a time for the state to come together."

The GOP and Democratic Senate campaign committees also announced they were temporarily suspending their advertising, as did Handgun Control Inc. and the Business Roundtable.

Carnahan, 66, his son and a campaign aide perished Monday night when the small plane they were flying went down in bad weather.

With three weeks remaining until Election Day, Secretary of State Bekki Cook said the governor's name would remain on the ballot. She added that if Carnahan wins the Senate election posthumously, the seat would become vacant in early January, after Ashcroft's current term ends.

At that point, Lt. Gov. Roger Wilson, a Democrat, would have the authority to appoint a senator to serve until a special election could be held in November, 2002.

Twice in the past year, possession of Senate seats has been affected by unexpected deaths.

Almost a year ago, on Oct., 24, 1999, Sen. John Chafee, R-R.I., died unexpectedly of heart failure. He had previously announced plans for retirement, and his son, Lincoln Chafee, was running to succeed him. But the death permitted the state's Republican governor to name the younger Chafee to the Senate, giving him the ability to serve for a year, and campaign as an incumbent.

At the same time, Democrats were forced into a long, divisive primary campaign before settling on a nominee, Rep. Robert Weygand. Party officials now say they have only modest hope of dislodging Chafee in November, even though Rhode Island is one of the nation's most Democratic states.

In July, Republican Sen. Paul Coverdell of Georgia suffered a stroke and died a few days later, with 4 years remaining in his term. The state's governor recruited former Democratic Gov. Zell Miller to take the position and to run for the remainder of the six-year term this fall.

Miller's commanding popularity discouraged several members of the state's House delegation from challenging for the Senate seat. Former GOP Sen. Mack Mattingly stepped forward, but privately, Republicans concede they have little chance of retaking a seat they once thought was safely theirs.

Democratic hopes for gaining control hinge on a series of races involving strong challengers to GOP incumbents, Ashcroft among them. Sen. Rod Grams in Minnesota; Spencer Abraham of Michigan; Conrad Burns of Montana; William Roth of Delaware and Slade Gorton of Washington are all battling to hold their seats. In addition, officials in both parties give Democrats a strong chance of capturing a seat in Florida, where GOP Sen. Connie Mack is retiring.

Republicans are not without opportunities for gains themselves. Virginia Democratic Sen. Chuck Robb has trailed his GOP challenger, former Gov. George Allen, in polls. Former GOP Rep. John Ensign has led in polling in Nevada, where a Democrat is vacating a seat. A Democratic open seat in Nebraska is competitive.

The GOP is also battling for Democratic open seats in New Jersey and New York, where Rep. Rick Lazio is running against First Lady Hillary Clinton.

The situation is further complicated, say strategists in both parties, by concerns over the health of Sen. Strom Thurmond, R-S.C., who is 97, has been hospitalized several times in recent months, and represents a state with a Democratic governor.

Political ambition also plays a factor in the battle for control of the Senate. Sen. Joseph Lieberman, the Democratic vice presidential candidate, is cruising to a new term in his Connecticut Senate seat.

He could withdraw as a Senate candidate and let the party replace him on the ticket. But Lieberman has given no indication he will do so, and Democrats worry that if he wins the vice presidency, Connecticut's governor will name a fellow Republican to the Senate seat.

Apart from the senatorial campaign, presidential campaign television advertising will stop running in Missouri, officials said. A resumption is likely sometime after Carnahan's funeral, scheduled for Friday.