(CNN) - As independent Republican groups pour more resources into West Virginia, a top non-partisan political handicapper now rates as a "toss up" the state's Senate battle, where the GOP hopes to capture a seat held by the Democrats for over half a century.
The Cook Political Report changed its outlook on the contest between popular two-term Democratic Gov. Joe Manchin and businessman John Raese, the Republican nominee, saying Thursday that, "the race that wasn't supposed to be competitive is now the contest that is too close to call today. It moves to the Toss Up column."
Another top non-partisan handicapper, the Rothenberg Political Report, lists the race as "Toss Up/Tilt Democrat."
Raese and Manchin face off in a special election in November to fill the final two years of the term of Democratic Sen. Robert Byrd, who died earlier this year. Byrd was first elected to the Senate in 1958.
On the same day that Cook changed its rating of the contest, American Crossroads announced it was beefing up its get out the vote efforts in West Virginia.
"West Virginia has emerged as a key state in the battle for control of the U.S. Senate and we are expanding our plans accordingly," said Steven Law, president and CEO of American Crossroads, in a release.
The group says West Virginia is the ninth state where they are investing in GOTV efforts. American Crossroads, which is also putting up ads in support of GOP candidates across the country, was launched this past spring by a group of influential Republicans. Their goal is to raise $52 million this year to help their party topple Democrats in the midterm elections. American Crossroads is likely competing with the Republican National Committee for many of the same donors.
Last week a leading conservative grassroots organization also announced it was taking aim at Robert Byrd's old Senate seat. FreedomWorks said it plans to support the Raese campaign with get-out-the-vote efforts "including direct mailings, yard sign distribution, volunteer phone banks and neighborhood literature drops leading up to election day," according to a statement.
The National Republican Senatorial Committee is on the air with both television and radio ads as well, in support of Raese, the president and chief executive officer of Greer Industries, which includes steel and mining operations.
Raese lost to Byrd in the state's 2006 Senate race.
Meanwhile, the Democratic Senatorial Campaign Committee is up with new ad in the state, attack Raese. And early last week Manchin won the endorsement of the U.S. Chamber of Commerce, becoming the first Democrat in a Senate contest to win the organization's approval.
A Democratic source acknowledges that the race has tightened in West Virginia but points to baggage that could hurt Raese in the final four weeks of the campaign.
Jesse Johnson of the Mountain Party is also on the ballot in the general election.
Follow Paul Steinhauser on Twitter: @psteinhausercnn