Sen. Ron Wyden insists he doesn’t have a grudge against fellow Democrat Dianne Feinstein of California. What he does have, though, is a hold on her two legislative priorities of the lame-duck session — and he has, in fact, placed a hold on every major bill coming out of her Intelligence Committee in the past two years.

Wyden’s moves to block the two latest bills — a spy agency reauthorization measure (S 3454) aimed at cracking down on leaks and an extension of expiring surveillance provisions from a 2008 law — are the newest demonstrations of how the Oregon Democrat has become the Senate’s hardest line to cross on civil liberties issues in the national security arena.

Wyden said he considers Feinstein a friend and that he has more in common with her than not as a member of her committee. And his stances aren’t about liberal versus conservative, he insisted, pointing to a record of working with Republicans on a variety of topics from taxes to health care. Indeed, the update of the 2008 surveillance law (S 3276) is even an Obama administration priority.

“I always start with the proposition that you try to find common ground,” he said. “Sometimes you have to stand alone. And often, when you stand alone on day one, as the debate evolves, you see how things — as you make your case — in effect come around your way, both in terms of policy and politics.”

Feinstein also emphasized her friendship with Wyden and said they have usually sorted out their differences. But that doesn’t mean the chairwoman of the Intelligence panel likes watching him slow her committee’s agenda. The 2008 law’s surveillance provisions, for instance, are set to expire at the end of 2012.

“It becomes a bit more difficult,” she said. “Ron has a position, and I respect that position. The majority of the committee feels differently, often a dominant majority.” Because several of the bills he has blocked emerged with near-unanimous support, she said she would prefer that he use “discretion” when he places a hold on legislation.

Even when Wyden isn’t blocking a national security bill over civil liberties issues, he is often a lonely voice of opposition. He was one of just five Democrats who voted Nov. 14 against advancing a cybersecurity bill (S 3414) backed by his party’s leadership and President Barack Obama. He has been among a small handful of Democratic senators seeking the Obama administration’s legal justification for the targeted killing of U.S. citizens suspected of being overseas terrorists, requests he said have gone unfulfilled.

But sometimes, his approach nets gains: His decision to block an earlier intelligence authorization bill over provisions aimed at cracking down on leaks resulted in the panel stripping the language so that it could advance on the Senate floor.

He also led the successful fight against a Senate anti-piracy measure that he said would impinge on free speech. Initially, the bill had broad Senate support, but later it was stalled by a grass-roots opposition campaign that saw numerous senators pull their backing.

Wyden’s stances have made him especially popular with civil liberties groups that have suffered a number of setbacks to their agendas as the federal government has sought new powers to hunt down terrorist suspects.

Michelle Richardson, legislative counsel in the American Civil Liberties Union’s Washington office, said Wyden has stepped into a leadership void on balancing civil liberties with national security needs left by the departure of former Sen. Russ Feingold, D-Wis.

Wyden’s approach, Richardson said, has been to try to enlist others in his cause. His staff has offered classified briefings to senators at times, and she said he has “serious intelligence chops” that make his peers take him seriously.

“There are probably a lot of people who you could say are a great lone voice or always vote the right way,” she said. “It’s another thing altogether if they’re good at organizing people to follow them.”

The holds he has placed on national security bills are not motivated by an urge just to arbitrarily block them, said Sharon Bradford Franklin, senior counsel for the Constitution Project.

“It’s very helpful for him to raise the profile and ask the Senate to not rush consideration of these bills when there are very serious civil liberties concerns,” Franklin said. Wyden’s hold on the extension of the 2008 surveillance law means the Senate will have to set aside floor time to debate the bill and consider amendments, a move Wyden said he welcomed.

Because of his state’s political demographics, a mix of urban liberalism and rural libertarianism, Wyden can be aggressive in his defense of civil liberties without facing loud charges from constituents that he is “soft on terrorism,” said Jake Weigler, who managed Wyden’s 2010 reelection campaign and now works for the public affairs firm Strategies 360.

“He grew up with those values, but sees them reflected in his home state,” he said. “It allows him to be more outspoken than senators in other states where it would be a political liability.”

Wyden said he inherited some of his civil liberties views from his father, a journalist. But he also said he has grown more worried recently about the balance between national security and civil liberties.

“I’ve come to feel in the last couple years that the constitutional teeter-totter is out of whack,” he said.

And despite Feinstein’s lament about the uptick in his use of holds, Wyden said he rarely catches heat from other senators or the administration when he gums up the works.

“I really don’t. I think there’s a recognition that I’ve had these views for a long time,” views that Wyden said Feinstein and others recognize as sincere. “I didn’t just wake up one morning and say, ‘I want to throw sand in the gears here.’”