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Former Vice President Dick Cheney's daughter Liz Cheney will run against her fellow Republican, senior Wyoming Sen. Mike Enzi, in next year's primary election.

Cheney, who plans to formally announce her Senate bid at a Wednesday press conference, described her conservative agenda and criticized President Obama's policies in a video released online by her campaign.

"President Obama has launched a war on our Second Amendment rights, he's launched a war on our religious freedom, he's used the IRS to launch a war on our freedom of speech and he's used the EPA to launch a war on Wyoming's ranchers, our farmers and our energy industry,'' she said.

Cheney's plans to run against Enzi has been an open secret for months. Her announcement is a political challenge unlike anything Wyoming has seen for years, maybe decades -- Republicans in the state rarely challenge incumbents in national office.

Enzi, apparently armed with the knowledge Cheney's announcement was imminent, also announced Tuesday he will seek a fourth term. Enzi made the announcement six months earlier than he has in the past, but says he will continue to "do the job I was already elected to do."

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    "Working behind the scenes -- this is what I have been doing since I was elected and this is what needs to be done," he said by email through his spokesman.

    Sen. Jerry Moran, R-Kan., who is the chairman of the National Republican Senatorial Committee, says the group plans to back Enzi in 2014 and Republican senators will stand behind their colleague.

    Rep. Cynthia Lummis, R-Wyo., also spoke out in support of Enzi, saying she doesn't believe Cheney is going about her candidacy "in the right way."

    "(Cheney) will out-raise (Enzi) by factors of ten or more and he will still win," Lummis said.

    Enzi takes pride in keeping a lower profile and remaining much less partisan than most of his colleagues. He often refers to his "80-20" rule -- that opposing parties usually can agree on 80 percent of the details of any given issue -- as a model for Republicans and Democrats to work together.

    He handily won re-election in 2008 with more than 75 percent of the vote.

    Chris Rothfuss, Enzi's Democratic challenger in that election, also spoke out in support of Enzi, saying Cheney's challenge reflects "everything that's wrong" with partisanship in national politics.

    "Mike's being attacked in this election because he's been traditionally willing to compromise and reach across the aisle in a manner that's unpopular with the partisan culture," he said.

    "I would also say that the reason that Liz Cheney is running out of Wyoming rather than what in effect would be her home state of Virginia is because we're basically seen as a much cheaper option in trying to obtain a Senate seat. Obviously, it's an attempt to leverage her name recognition," said Rothfuss.

    Alan K. Simpson, a former U.S. Senator from Wyoming and a longtime observer of state politics, said Tuesday he couldn't comment on what the race would mean for the Wyoming Republican Party.

    "Right now, I have nothing to say at all except one thing, I deeply care about both of them, and that's all I have to say," Simpson said of Enzi and Cheney.

    Enzi, a former state legislator and mayor of Gillette, was first elected to the Senate in 1996.

    Cheney, who is married and has five children, holds a law degree from the University of Chicago and has worked for the State Department and the Agency for International Development. She has been in the public eye in recent years as a Fox News political commentator.

    The Cheneys are well-established as a family with Wyoming roots -- an important qualification for anybody seeking major office in the state. Her announcement release pointed out that the Cheney family goes back more than 100 years in Wyoming.

    Dick Cheney represented Wyoming in the House for 10 years, from 1979 to 1989.

    The Associated Press contributed to this report