Democratic challenger Kay Hagan knocked off Republican Sen. Elizabeth Dole in North Carolina's Senate race, the fourth pickup in what is unfolding as a big night for Senate Democrats.

Hagan, 45, a five-term state senator, now becomes North Carolina's second female senator in the traditionally Republican state. With 4 percent of the precincts reporting, Hagan was up 59-38 percent against Dole.

Also riding that wave was former New Hampshire Gov. Jeanne Shaheen, who defeated first-term Sen. John Sununu (R) in that state, Democrat Mark Warner, the former governor of Virginia who won that state’s open Senate seat, Rep. Tom Udall (D), who coasted into New Mexico's open Senate seat to replace retiring Republican Pete Domenici, and his cousin, Rep. Mark Udall, who won the open Senate seat in Colorado.

Warner defeated Republican Jim Gilmore, also a former governor, in the fight for the seat held by retiring Sen. John Warner (R), a five-term senator and one of the chamber’s most respected voices on foreign policy. Warner's victory represents a Democratic transformation of a state that was dominated by Republicans just four years ago.

Republicans did manage to hold Democrats off from stealing the biggest prize in this year's Senate races: GOP Leader Mitch McConnell won a fifth term over Democratic challenger Bruce Lunsford, holding a 51 to 49 percent lead with nearly 60 percent of precincts reporting.

But that wasn't enough to stop momentum elsewhere in what is expected to be a big night for the Democratic Party, which is aiming for a robust majority with as many as 60 seats to help overcome the use of filibusters to derail legislation. With Tuesday's wins, Democrats hold a 56-44 Senate majority, with two independents who caucus with them.

Mark Warner, who is not related to John Warner, is a rising star in the Democratic Party. Having toyed with mounting a presidential bid in 2008, the former Virginia governor later decided instead to run for the Senate. This is not his first foray into Washington politics, however. After obtaining his law degree from Harvard University, Warner worked on the staff of Sen. Chris Dodd (D-Conn.) in the early 1980s.

After leaving Capitol Hill and making a fortune in a telecommunications firm, he unsuccessfully ran for the Senate in 1996 against John Warner. In 2001, he became governor of the once GOP-dominant state and left office with high favorability ratings. His stature has since skyrocketed in Democratic circles, and he delivered the keynote address at the party’s 2008 nominating convention.

Polling has found Democratic challengers ahead in other states — Alaska, Minnesota and Oregon. Polls close at 9 p.m. in Minnesota. In Oregon, polls in the eastern part of the state close at 10 p.m., and at 11 p.m. in the western part of the state.

In Alaska’s Senate race, in which the longest-serving Republican in history, Ted Stevens, is trying to hold onto his seat of 40 years despite his felony conviction, polls close at midnight in the eastern part of the state and 1 a.m. in the western part.