WASHINGTON — Describing herself as “thankful and blessed,“ Sen. Olympia Snowe reflected on four decades in elective office and shared her hope that the U.S. Senate will rediscover “the art of legislating” during a farewell address Thursday afternoon from the floor of the chamber where she served for the past 18 years.

Snowe, a Republican, departs after serving in Congress longer than all but two women in U.S. history. She first won the right to represent Maine’s 2nd Congressional District in 1978. She served in the House until 1994, then won election to the Senate, defeating 1st District U.S. Rep. Tom Andrews, a Democrat, for the right to succeed Democrat Sen. George J. Mitchell, who chose not to seek re-election.

Snowe easily won re-election in 2000 and 2006. She became Maine’s senior senator in 1997 and, with fellow Republican Susan Collins, extended Maine’s reputation for moderation and independence in an increasingly partisan Congress.

In February of this year, Snowe sent tremors across Maine’s political landscape by announcing that she would not to seek a fourth term. She cited a toxic, unproductive environment in Congress as the chief reason for her decision not to seek re-election.

During Thursday’s approximately 30-minute speech, Snowe expressed gratitude to staff, colleagues and family for the support they have shown her throughout her political career. Noting that she and her husband, former U.S. representative and Maine Gov. John McKernan, can claim 56 years of combined service in public office, she joked that the couple defined free time as “listening to each other’s speeches.”

“We’ve had a passion for public service … and we’ve never regretted a single moment,” she said.

But it was the people of Maine who merited Snowe’s greatest praise and gratitude.

“I first and foremost want to thank the people of Maine for allowing me to be their voice, their vote, and their champion for 16 years in the U.S. House of Representatives, and for three terms in the U.S. Senate,” she said. “One of the definitions of the word ‘trust’ is ‘a charge or duty imposed in faith or confidence.’ And to have had the trust of Maine people, who have placed their faith and confidence in me, is an honor of indescribable magnitude. Indeed, serving my magnificent state over the past 34 years in the halls of Congress has been the greatest privilege of my life.”

Citing inspiration from Margaret Chase Smith, who also represented Maine in the U.S. House and Senate, Snowe listed a series of legislative accomplishments that she said were achieved by consensus and in an evenhanded manner consistent with Maine values. She reflected on her early membership in a bipartisan caucus on women’s issues.

“We couldn’t draw political lines in the sand,” she said of working with Democrats such as former Rep. Patricia Schroeder, D-Colo., and Sen. Barbara Mikulski, D-Md., who like Snowe advanced from the U.S House to the Senate. “When we spoke on these issues, we spoke as women, not Democrats and Republicans.”

Snowe focused much of her speech on the need for greater coalition building and bipartisanship within the Senate.

“Arriving at compromise wasn’t always easy by any means,” she said. “Because it is only when we minimize the political barriers that we can maximize the Senate — allowing it to become an unparalleled incubator for results that truly matter to the American people.”

She also reiterated her reasons for choosing not to seek re-election.

“Throughout my tenure, I’ve borne witness to government’s incredible potential as an instrument for common good,” she said. “I have also experienced its capacity for serial dysfunction. Indeed, as I stated in announcing I would not seek a fourth term in the U.S. Senate, it is regrettable that excessive political polarization in Washington today is preventing us from tackling our problems at a time of monumental consequence for our nation.”

Voicing her fear that “we are losing the art of legislating,” Snowe urged her colleagues to recommit to following “the Founding Fathers’ blueprint, in order to return the institution to its highest calling of governing through consensus. For it is only then that the U.S. Senate can ascend to fulfill the demands of our times, the promise of our nation and the rightful expectations of the American people.”

Doing so is particularly urgent as the lame-duck Congress in which she serves seeks a way to avoid the so-called “fiscal cliff” of tax increases and automatic federal program cuts that will take effect Jan. 1 and which economists fear will plunge the country back into recession.

“For the sake of the country, we must demonstrate to the American people that we are capable of making the big decisions” to avoid the fiscal cliff before the end of this year,” she said.

Immediately after Snowe’s speech, two Democrats from across the aisle offered praise from the Senate floor. Sen. Mary Landrieu, D-La., described Snowe as “a clarion call for common sense and common ground in a place that’s getting harder to find those things every day” and “a unique talent who has served this country.” Mikulski added that Snowe’s “duty-driven approach” and penchant for “getting the job done in a way that’s inclusive” have benefited the entire country.

Maine Gov. Paul LePage praised Snowe as “a wonderful public servant for the people of Maine and the nation” in a release issued after her speech.

In September, Snowe announced she intends to write a book next year. She also plans to work for greater civility in politics, which she reaffirmed Thursday.

“I’m not leaving the Senate because I’ve ceased believing in its potential, or I no longer love the institution — but precisely because I do,” she said. “I’m simply taking my commitment to the Senate in a different direction. I intend to work from the outside, to help build support for those in this institution who will be working to re-establish the Senate’s roots as a place of refuge from the passions of politics, as a forum where the political fires are tempered, not stoked — as our Founding Fathers intended.”

In addition to her 34 years in Congress, Snowe served in the Maine House of Representatives from 1973 until 1978.

Independent former Gov. Angus King won a five-person race in November to succeed Snowe. He will be sworn in Jan. 3, 2013.