Democrats were projected to add at least five seats to their majority of 51-49 with two Independents caucusing with Democrats.

In one of the biggest upsets of the night, state Sen. Kay Hagan ousted incumbent Republican Sen. Elizabeth Dole in North Carolina.

In another upset, former Democratic New Hampshire Gov. Jeanne Shaheen won a close Senate race, unseating Republican incumbent John Sununu.

The only Democratic seat considered in jeopardy, Sen. Mary Landrieu of Louisiana retained her seat.

Senate Minority Leader Mitch McConnell of Kentucky held off a challenge by Louisville businessman Bruce Lunsford.

Early results indicated Republican Idaho Lt. Gov. Jim Risch was poised to beat out Democratic former Rep. Larry LaRocco in the state's U.S. Senate race Tuesday to replace retiring Larry Craig, whose arrest in a Minneapolis airport bathroom sex sting captured national headlines last year.

The closely watched U.S. Senate race in Colorado appeared to end Tuesday with Democrat Mark Udall besting Republican Bob Schaffer to replace the retiring GOP Sen. Wayne Allard, early results show.

Republicans Mike Enzi and John Barrasso won re-election to the U.S. Senate Tuesday in Wyoming.

Democrat Frank Lautenberg, at 84 the third oldest member of the U.S. Senate, won a fifth term Tuesday in New Jersey.

In Virginia's open seat, Democrat Mark Warner defeated Republican Jim Gilmore Tuesday to win the seat held by retiring Sen. John Warner, R-Va.

In Minnesota, Republican incumbent Sen. Norm Coleman held a slight edge over Democrat Al Franken of "Saturday Night Live" fame.

Convicted felon Sen. Ted Stevens, R-Alaska, also was slightly ahead of Anchorage Mayor Mark Begich in his re-election bid.