Privately, Republicans and Democrats both said Wednesday that her win had probably made Kerrey's comeback more difficult.
North Dakota looked like a sure thing for Republicans when Democratic Sen. Kent Conrad announced plans to retire.
But Democratic challenger Heidi Heitkamp, a former attorney general, is credited with running a strong campaign that even Republicans concede has made her race against Rep. Rick Berg a competitive one — even though the state is expected to vote heavily for Romney this fall. At a minimum, the GOP and allied groups are likely to be forced to spend money on television advertising that once seemed unnecessary.
In Missouri, a three-way Republican primary is on the horizon, but already Sen. Claire McCaskill is rated among the most endangered incumbents of either party. Unlike other Democrats in tough races, she probably won't benefit from the White House race, since Obama appears unlikely to spend time or money in the state.
In Montana, Democratic Sen. Jon Tester has been defending his seat against a challenge from Rep. Dennis Rehberg in a race that is expected to remain close through Election Day.
Democrats' chances got a lift in Maine with Sen. Olympia Snowe's decision to retire, although they still have virtually no chance of winning the seat outright.
The primaries won't be held until August, but former Gov. Angus King's decision to run as an independent has overshadowed all other events. He won't say which party he would side with if elected to the Senate. Republicans say they doubt it would be them and have encouraged speculation it would be the Democrats, an apparent attempt to sully his chances.
In Massachusetts, Democrats viewed Republican Sen. Scott Brown as an interloper after he won the race to fill out the unexpired term of the late Sen. Edward M. Kennedy. They eagerly recruited Elizabeth Warren to run after Republicans blocked her nomination to a consumer protection post in the Obama administration.
Warren has raised more money than Brown since joining the race, pulling in $15.8 million as of her most recent report to the Federal Election Commission. But she has stumbled recently following the disclosure that she had listed herself as having Native American heritage in law school directories.
In Nevada, Democratic hopes rest on the party's ability to defeat appointed Sen. Dean Heller. Two years ago, the GOP chances of winning a seat vanished when tea party-packed challenger Sharron Angle emerged from a primary.
This year, Indiana appears the state likeliest to test the Democratic claim that tea party candidates hurt the Republicans — as happened in Delaware, Colorado and Nevada in 2010.
State Treasurer Richard Mourdock defeated six-term Sen. Lugar in the GOP primary and will face Rep. Joe Donnelly in the fall. Democrats say the race is winnable, and Republicans concede that, as elsewhere, they are likely to have to spend campaign funds to make sure the seat stays in their column.
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