WASHINGTON (Reuters) - Republican U.S. Senator Lisa Murkowski, an unpredictable moderate in a polarized Washington, on Monday declared she will vote to acquit Donald Trump, but not before leveling an attack against the president and fellow lawmakers of both parties during a partisan impeachment ordeal.

“The president’s behavior was shameful and wrong. His personal interests do not take precedent over those of this great nation,” Murkowski declared in a speech to a near-empty Senate chamber.

On Wednesday the Senate is scheduled to wrap up a two-week impeachment trial and vote to either acquit or convict Trump on charges leveled by the Democratic-controlled House of Representatives that the Republican president abused his powers and obstructed Congress’ investigation of his dealings with Ukraine.

It was no surprise that the 62-year-old senator attacked House Democrats, accusing them of a slapdash investigation of Trump’s actions toward Ukraine and his alleged withholding of U.S. aid in order to pressure Kiev to investigate one of his political rivals, former Vice President Joe Biden, a contender for the Democratic presidential nomination.

But Murkowski, with her fellow senator from Alaska presiding over the chamber after other senators had left for the night, took on not only Trump, but also fellow Republicans, Senate Democrats and the media.

Alluding to a “demon” burning its way through Washington during the impeachment process that began late last September, Murkowski blamed “a careless media” that she said “cheerfully tried to put out the fires with gasoline.”

Long one of the few moderate voices in the Senate, Murkowski shocked the political establishment in 2010 when she became the first senator in more than 50 years to win re-election with a write-in campaign after the Republican Party tried to dump her in favor of a more conservative challenger.

In the summer of 2017, Murkowski again was in the spotlight when she and two other moderate Republican senators -- Susan Collins and the late John McCain -- ruined Trump’s push for a partial repeal of the “Obamacare” healthcare law.

On Monday she said, “I cannot vote to convict” Trump, and indicated a preference for a much softer penalty than the removal from office that Democrats have been clamoring for -- a “censure” by Congress.

She went on to list transgressions on both sides of the political divide that she saw unfolding during this impeachment process, only the third in U.S. history:

She cited Trump supporters’ eagerness to “have just dismissed the case as soon as it reached” the Senate and Trump’s detractors’ acting as if “the only way the trial could have been considered fair was if it resulted in the president’s removal from office.”

With a broad-brush criticism of both political parties, Murkowski spoke of their “apparent willingness...to destroy not just each other, but all of the institutions of our government. And for what? Because it may help win an election?”

Having castigated the House, the Senate, Trump and the media, Murkowski wrapped up her approximately 11-minute diatribe on a note of faint optimism: “It’s my hope that we finally found bottom here.”