HELENA (AP) -- Rep. Denny Rehberg staved off an opponent's attempt to capitalize on a national surge in conservatism and voter anger toward incumbents, easily winning the Republican primary Tuesday in his bid for a sixth term as Montana's sole congressman.

Rehberg defeated political newcomers Mark French, a laboratory scientist from Paradise, and A.J. Otjen, a marketing professor at Montana State University-Billings. He now goes on to face the winner of the Democratic primary in the Nov. 2 general election.

"I don't think that anybody missed the message that the electorate and Montanans, as well, are upset with the direction of the country," Rehberg said Tuesday night from Washington, D.C. "I just appreciate Montanans giving me a vote of confidence to carry the banner forward."

French had tried to tap into a tea party-led conservative surge by painting himself as a far right "constitutional candidate," and portraying Rehberg as a Washington insider complicit in the federal government's intrusion into ordinary Americans' lives.

"These people are waking up, and they're learning about the constitution," French said. "They're seeing the degradation of our nation into socialism. They're a group of people wanting to take our country back, and I support them."

But Rehberg wasn't as vulnerable as GOP incumbents in other races around the country, said James Lopach, chairman of the University of Montana political science department. He is a small-government, low-tax, minimal-regulation Republican who hasn't done anything to anger anybody to his political right, Lopach said.

"It would be hard for a primary opponent to drive a wedge between him and the right wing of his party," Lopach said.

With 620 of 792 precincts reporting, Rehberg captured more than 75 percent of the vote, compared with just under 19 percent for French. Otjen won less than 6 percent of the vote.

Rehberg, 54, is a former lieutenant governor, a three-term state legislator and rancher who has been Montana's congressman since 2001. He was born in Billings, and he and his wife, Jan, have three children.

Rehberg himself has said he may not be the most conservative Republican in Congress, but he has a long record of advocating for conservative principles, dating back to his days in the state Legislature in the 1980s.

The third candidate in the race, Otjen, ran as a more liberal "Teddy Roosevelt" Republican, with endorsements from such groups as Republicans for Environmental Protection. She was the only one in the primary saying that cutting taxes while raising spending is a poor way to grow the economy and get the country out of debt.

Rehberg will begin the general election campaign with a substantial war chest; he has raised nearly $1 million and had more than $725,000 in the bank at the beginning of June.

By comparison, the two leading Democrats have spent most of what they have trying to escape their own primary. Dennis McDonald, the state Democratic Party chairman from 2005-2009, had raised $167,718 by the end of May but had just over $11,000 left in the bank. Missoula attorney Tyler Gernant also has spent nearly all the $124,500 that he has raised.

Rehberg made headlines when a Flathead Lake boat crash injured him and left an aide in a coma for more than a week. He was onboard the boat piloted by state Sen. Greg Barkus of Kalispell, who has been charged with criminal endangerment and two counts of negligent vehicular assault for allegedly drinking while driving the vessel.

His opponent in the general election may try to use the boat crash during the campaign, but Lopach said he doesn't see the crash as an obstacle that will take a significant number of votes away from Rehberg.

"I just can't see how that can be laid on him," Lopach said.