(CNN) - Is the Nebraska battle to succeed retiring Democratic Sen. Ben Nelson tightening up?
Republican state Sen. Deb Fischer is considered the clear favorite over her Democratic opponent, former Sen. Bob Kerrey, but a new poll suggests Kerrey is closing the gap. And a conservative super PAC that supports Republican candidates is going up with a new ad buy in the state in support of Fischer.
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According to a poll from the Omaha World-Herald, 48% of likely Nebraska voters support Fischer, who in May pulled an upset to win a crowded GOP primary, with 45% backing Kerrey, the state's former governor and two-term U.S. senator. Fisher's three point edge is within the survey's sampling error, and is down from a ten point lead in the Omaha World-Herald's previous poll.
The poll's release comes as American Crossroads begins running ads backing Fischer. The spots appear to be the first ones from a major national outside organization.
"Nebraska is a 'must-win' race for Republicans so it shouldn't surprise anyone to see folks on our side reminding voters in the closing days of Bob Kerrey's very liberal views. But given that national Democrats aren't investing resources here, it's clear they do not see a path to victory for their side," National Republican Senatorial Campaign Communications Director Brian Walsh told CNN.
Meanwhile, Tuesday Fischer's campaign emailed out a release trying to tie Kerrey to Senate Majority Leader Harry Reid, the top Democrat in the chamber.
National Democrats see the poll as evidence that they can keep party control of Nelson's seat.
"Nebraskans knew virtually nothing about Deb Fischer, and the more voters learn, the more they are rejecting her. Bob Kerrey has closed this race and that is why you are seeing Karl Rove and super PACs begin to panic," Democratic Senatorial Campaign Committee Executive Director Guy Cecil told CNN.
The Democrats currently control the Senate 53-47. But they are defending 23 (21 Democrats and two independents who caucus with the party) of the 33 seats up for grabs in next Tuesday's election.