HELENA -- Driving his tractor-trailer rig to various campaign stops on Tuesday, Democrat Jon Tester, a Big Sandy farmer and state Senate president, launched his candidacy for the U.S. Senate seat held by Republican Conrad Burns.

Joined by his family and Sen. Ken "Kim" Hanson, D-Harlem, who helped with the driving, Tester drove to Havre and then to Billings on Tuesday. He plans stops in Bozeman, Butte and Missoula today and in Helena and Great Falls on Thursday.

Tester, 48, said in a cell phone interview from his truck that he is seeking the U.S. Senate seat because he believes many Montanans have been overlooked by the federal government.

"I just feel small business, family farmers, agriculture, working people have been kind of under attack for the last 15 to 20 years," Tester said. "I think the federal government needs top make these people a priority. The middle class has built this country, and we need to make them whole."

Other top issues, he said, are opposing President Bush's Social Security plan to let some people put some of their Social Security money instead in private investment accounts, and the soaring federal deficit, which threatens Medicaid and highway funding.

"More than half of our (state budget) money is federal," he said. We've got to work to protect them."

Tester said he will be trying to raise the $600,000 to $800,000 that people have told him he will need for the primary election. Defeating Burns in the general election will take at least $6 million, he said.

"We'll handle the money as frugally as we can," Tester said. "We'll do the best we can with what we have to work with. I'm used to working with budgets that are pretty close to the table."

Tester is a former school music teacher who is an organic grain farmer. He served on the Big Sandy school board before serving four sessions in the Montana Senate, most recently as Senate president.

He is the third Democrat to declare his candidacy for the Senate seat, joining state Auditor John Morrison, 43, of Helena and Clint Wilkes, 55, a political newcomer from Bozeman. Other Democrats who have expressed interest in the race but not yet declared are former House Speaker and Missoula Mayor Daniel Kemmis, 59, of Missoula, and former state Rep. Paul Richards, 50, of Boulder.

Burns, 70, will be seeking his fourth Senate term and already has raised $2.22 million so far and had $1.5 million in the bank as of March 31.

Tester conceded that defeating Burns would be difficult, but not impossible.

"I think he's kind of lost touch with Montana," Tester said. "He's made some bad votes on Amtrak and farm programs the last few months."

Said Burns: "I look forward to watching a spirited Democratic primary, and should Mr. Tester be the Democratic nominee, when it gets time to start the campaign, Montanans will see that we have two very different philosophies."

As for Morrison, an attorney is serving his second term as the state auditor regulating insurance and securities in Montana, Tester said, "Morrison's a good guy. We're totally different individuals. I'm an aggie. My family's been in the state three generations, my wife's family four generations. I'm a small business owner and an ag person that's had to make his living off the land."

Morrison, in turn, called Tester "a good state senator" and said "his interest and other people's interest in this race just goes to show that Conrad Burns is on his way out.:

"The people of Montana have elected me twice statewide, and I'll be proud to run on my record over the last five years," Morrison said. "We've worked to provide affordable health care, to prosecute fraud, protect consumers and promote small business, and that's what I'm going to continue to do."

Tester said he decided to jump into the Senate race because of the strong support he received from fellow Democratic legislators, constituents and folks around the state.