Rep. Denny Rehberg is viewed as the early frontrunner to challenge Democratic Sen. Jon Tester next cycle, and while the Montana Republican not may not decide whether to enter the race until 2012, at least two other Republicans are weighing campaigns.

Steve Daines, the 2008 lieutenant governor nominee, said in an interview last week that he is considering a Senate bid. Republicans in the state expect him to announce he’s running this weekend.

Montana state GOP Executive Director Bowen Greenwood said Monday that Daines sent out a “big mailer” recently noting that there would be an announcement Saturday regarding his political plans. “It’s not a very well kept secret that it will be the Senate,” Greenwood said.

Neil Livingstone, a national security and terrorism expert, also told Roll Call recently he is considering a Senate run.

Livingstone said he has “great concern about the way the country is going, so I’m taking a serious look at it.”

After picking up six Democratic Senate seats last week, Republicans are rolling into what appears to be another favorable election cycle. Tester is among Republicans’ top targets, along with several other first-term Senators from the 2006 class.

A spokesman in Rehberg’s Congressional office said the Congressman was not thinking about a possible Senate bid at this point. But Republican insiders say that all eyes are on Rehberg, who is a former lieutenant governor and represents the entire state in an at-large district.

The Congressman, who was just elected to a sixth term with 60 percent of the vote, is known to have higher office ambitions and as of mid-October he had $616,000 in his campaign account. Tester showed $503,000 on hand as of Sept. 30.

But Rehberg’s competition for the GOP nomination is getting organized early. Livingstone has a political action committee, Livingstone4Montana, which had raised nearly $30,000 by the end of September.

Livingstone is CEO of ExecutiveAction, a Washington, D.C.-based crisis management firm, and he is a regular TV commentator on terrorism issues. Livingstone said he was raised in Montana, and still votes and spends most of his time in the state, where he owns a home.

“I’ve been urged by a variety of people to look at this as a possible race,” Livingstone said. “I probably won’t make a decision until late spring.”

Daines is a businessman and currently serves as vice president at RightNow Technologies. He also served as state chairman for the 2008 presidential campaign of former Arkansas Gov. Mike Huckabee (R).

Tester ousted Republican Sen. Conrad Burns in 2006. Despite being outspent by $3 million, Tester highlighted Burns’ ethics issues and won by fewer than 4,000 votes out of nearly 400,000 cast.