Last spring, Sen. Frank Lautenberg (D-N.J.) decided he’d had it with Republicans questioning the military service and patriotism of his Senate colleague, the Democratic presidential nominee John Kerry (Mass.).

As Lautenberg’s aides tell it, the 81-year-old World War II veteran strode into his office suite on the morning of April 28, 2004, with a plan to go to the Senate floor and make a statement in defense of Kerry’s record in Vietnam.

But he didn’t want his speech to get lost in the chamber’s verbose ramblings.

“He said, ‘I want to deliver a speech that will draw the lines between those that, when their country needed their service, didn’t serve, and those that did,’” said Lautenberg spokesman Alex Formuzis.

Later that day on the Senate floor, Lautenberg drew widespread criticism from his Republican colleagues — and muted applause from Democrats — for explicitly calling Vice President Cheney a “chickenhawk” for receiving multiple deferments during the Vietnam War and implying that the description also fit President Bush, who rode out the war in the Texas Air National Guard.

Pointing to a poster with a cartoon chicken dressed in military garb, Lautenberg said, “Chickenhawks shriek like a hawk, but they have the backbone of a chicken. … They always talk tough on national defense and military issues and cast aspersion on others. When it was their turn to serve, where were they? A-W-O-L, that’s where they were.”

Calling the vice president a charlatan from the well of the World’s Greatest Deliberative Body was a bold and inflammatory move for a man whose career had been largely overshadowed by more famous New Jersey Senators, especially former pro basketball player Bill Bradley (D) and the scandal-ridden Robert Torricelli (D), whom Lautenberg came out of a short-lived retirement to succeed in 2002.

But after two decades in the Senate, it’s Lautenberg’s new, no-holds-barred, blunt-talking style that now makes him one of the most outspoken — and liberal — Senators currently serving. In fact, even the “liberal lion,” Sen. Edward Kennedy (D-Mass.), has deferred to Lautenberg on critiquing the Bush administration’s use of government funds for so-called “covert propaganda.”

During his first three terms in the Senate, Lautenberg was better known as a stately fiscal moderate and consensus-seeking dealmaker who spent much of his time gaining seniority on powerful committees, most notably the Appropriations Committee, where he was well-positioned to send “pork” back home to New Jersey.

Senate hands sense a very different lawmaker now. “He used to be a lot more careful,” said one Democratic leadership aide. “He’s gotten a lot more partisan over the past few years.”

After a two-year retirement, Lautenberg came back to the Senate a lowly freshman — in a Senate where Democrats had just lost their narrow majority, making the party unable to provide Lautenberg with his old seniority or his old assignments on top-tier committees.

Now, Lautenberg is relegated to junior postings on less influential panels such as the Commerce, Science and Transportation Committee and the Homeland Security and Governmental Affairs Committee, despite having saved the New Jersey Democratic Party’s bacon after Torricelli — Lautenberg’s political nemesis — quit his re-election bid just a month before the election.

“It wasn’t easy, because, very frankly, I had some illusions or delusions that some of the seniority and the committee placements would have been better” handled, Lautenberg said in a recent interview.

Without the responsibility of serving as ranking member of the Budget Committee or the Appropriations subcommittee on Transportation, Lautenberg found himself with a lot more time to express his outrage at Republican policy priorities and what he sees as the questionable ethics of the Bush administration.

“I think coming back to the Senate with so much experience and not gaining his seniority back allowed him to use his expertise to investigate this administration, and that became a focal point for him,” said Dan Katz, Lautenberg’s chief counsel. “In his first terms, he had responsibilities linked to seniority that didn’t allow him to do these things.”

The Democratic leadership aide agreed. “He had already established a long legacy on a number of key issues, and when he came back, he saw a need to speak out more forcefully. … It stands out at a time when other Democrats are afraid to do that.”

Indeed, the Kerry campaign often called on Lautenberg to defend the Democratic presidential candidate in 2004, and he “won a lot of plaudits from in the party,” the Democratic leadership aide said.

But lest folks assume that Lautenberg’s new outspokenness comes from the knowledge that he won’t run for re-election in 2008, Lautenberg says think again.

“A lot of it depends on … can I maintain my surliness?” said Lautenberg of making another run at age 84. “But I like being back here, I must tell you. I feel right about the things I’m doing.”

Indeed, Lautenberg started up a campaign committee again in 2003 and is raising money, presumably for a fifth term. But four years out, his fundraising totals are still modest for an expensive campaign in New Jersey, where television time must be bought mostly on pricey New York and Philadelphia stations. Lautenberg raised almost $670,000 as of the end of last year, according to Formuzis.

Republicans aren’t exactly cheering Lautenberg’s turnabout from mild-mannered dealmaker to partisan pit bull.

“It’s unfortunate that he has taken on this newfound role of attack dog,” said one Senate Republican leadership aide. “Prior to his retirement, which was four years ago, he seemed much more tempered.”

But eight months after the “chickenhawk” speech, Lautenberg said he doesn’t regret causing a furor in the Senate with his frank choice of words.

“It infuriated me that people who dodged — and I use that word advisedly — dodged the charge to serve are now chickenhawks,” Lautenberg said.

It’s that sense of outrage that has fueled numerous other Lautenberg stunts, such as when he was the first of his colleagues to take to the Senate floor in February 2004 to upbraid Republican lawmakers, especially Sen. Saxby Chambliss (R-Ga.), for suggesting that Kerry was weak on national security.

While he didn’t specifically name Chambliss on the Senate floor — doing so would have been a serious no-no under Senate rules — Lautenberg referenced what he views as Chambliss’ draft-dodging actions during the Vietnam era.

“It is the same easy road we see when someone files for five student deferments and then claims an old football injury should prevent him from fighting for his country,” Lautenberg said in response to Chambliss’ criticism of Kerry’s candidacy. Chambliss had already earned the enmity of Democrats in 2002 for ousting then-Sen. Max Cleland (D-Ga.) with the help of an ad that appeared to link the Vietnam-era triple-amputee with Saddam Hussein and Osama bin Laden.

Lautenberg has also been at the forefront of requesting investigations into the Bush administration’s use of taxpayer dollars to promote its initiatives, including the recent revelation that conservative commentator Armstrong Williams did not disclose that he took money from the Education Department to promote Bush’s signature education initiative, No Child Left Behind.

Lautenberg’s persistence on these issues has resulted in several opinions by Congress’ independent investigative arm, the Government Accountability Office, that determined the Bush administration violated a law prohibiting the use of appropriated funds for “publicity and propaganda” purposes, or as GAO has called it, “covert propaganda.”

The GAO made those findings after Lautenberg and other Democratic lawmakers asked GAO to look into the legality of video news releases used to promote, among other things, the Medicare prescription drug law.

Another favorite Lautenberg target is Sen. Sam Brownback (R-Kan.), who over the past few years has used his position as chairman of the Commerce subcommittee on science, technology and space to hold hearings on issues of special interest to social conservatives, such as the dangers of abortion and stem-cell research.

Whenever Lautenberg believed Brownback was distorting the jurisdiction of the subcommittee, on which Lautenberg sits, the feisty Democrat would show up to Brownback’s hearings to chide him.

“Science and technology is talking about the aftermath of an abortion and how painful it was?” an incredulous Lautenberg asked in an interview. “The idea that it’s a matter of jurisdiction [for the subcommittee], when it clearly isn’t, … that’s been a personal thing for me.”

Meanwhile, Lautenberg plans to throw himself into the Senate Democratic Policy Committee’s new Investigations Committee, which Chairman Byron Dorgan (D-N.D.) set up to counter what many Democrats believe is Republican resistance to investigating allegations of misused taxpayer funds and cronyism by the Bush administration.

Lautenberg will regain his status as senior Senator if Sen. Jon Corzine (D-N.J.) wins this year’s gubernatorial race. As Corzine gets into an increasingly contentious primary race against acting Gov. Richard Codey, Lautenberg’s penchant for straight talk will likely make him a go-to guy when things need to be said that Corzine either can’t or won’t say himself.

Lautenberg endorsed Corzine last week and will serve as his campaign chairman.

Of course, throughout everything, Lautenberg said he is still attending to New Jersey’s needs and is using his old Senate friendships and alliances to get things done for his state.

“I think it was an advantage [as a freshman], because (a) I knew what I didn’t have and that inspired me, and (b) I know how things work and know when and where the right kind of pressure can be applied in a minority position,” Lautenberg said.