The White House is seen in Washington D.C., the United States, on Dec. 18, 2019. U.S. Democrat-led House of Representatives is engaging in a heated, polarized floor debate that will last for several hours on articles of impeachment ahead of historic impeachment votes over President Donald Trump on Wednesday. (Photo: Xinhua)

 As an hours-long US House debate on impeachment articles nears its end Wednesday, a much-anticipated vote that follows will decide whether Donald Trump will become the third US president to be impeached in US history.

The floor debate, set to last six hours equally divided by Democrats and Republicans, rehashed familiar arguments along party lines about Trump's dealings with Ukraine and the House Democrats' dealing with impeachment proceedings since Speaker Nancy Pelosi initiated the impeachment inquiry in late September.

"As Speaker of the House, I solemnly and sadly open the debate on the impeachment of the President of the United States," Pelosi said when kicking off the debate early in the day. "He (Trump) gave us no choice."

The president "tried to cheat. He got caught. He confessed. And then he obstructed the investigation," Democratic David Cicilline said during the debate, echoing the party's major tune that the impeachment against Trump is a war to defend US democracy.

"We feel very strongly that we are compelled by our duty to our oath and the Constitution and our democracy to act today where we have found that the President of the United States has abused his power," House Majority leader Steny Hoyer said as the House opened on Wednesday.

Across the aisle, House Republicans stand united behind Trump, slamming Democrats for weak and thin evidence behind their impeachment effort aimed to overturn the results of the 2016 presidential election.

"The American people see through this sad charade for what it is: an attempt to undo the 2016 election based on hearsay and opinion," said Ross Spano, a Republican from southeastern US state Florida.

No House Republican is expected to support impeachment, while a clear House majority including many centrist Democrats was ready to vote to impeach the president, according to multiple local media tallies.

Prior to and amid the House debate before the historic impeachment vote, Trump continuously issued or retweeted tweets from early Wednesday morning, calling Democrats' impeachment effort "an assault" on the country as well as on the Republican Party.

"SUCH ATROCIOUS LIES BY THE RADICAL LEFT, DO NOTHING DEMOCRATS. THIS IS AN ASSAULT ON AMERICA, AND AN ASSAULT ON THE REPUBLICAN PARTY!!!!" he wrote in all capital letters shortly after the debate began.

Outside the White House and Capitol, the US public seems almost evenly split over whether Trump should be impeached and removed from office.

As the House lawmakers debated, a group of people supporting the impeachment gathered outside the southeastern entrance of the Capitol on Wednesday afternoon, waving signs and banners that read "Country over Party," "Criminal in Chief," and "Fake President."

"Trump is abusing his power as the president for his own personal gain and to gain advantage in the elections," Terrie Waters, a demonstrator from Virginia, told Xinhua.

"Trump's behavior didn't leave Democrats a choice," said Waters, though she expected the Republican-controlled Senate not likely to convict the president.

Tom Kurzeja, a Trump supporter from Rockville, Maryland, told Xinhua he opposes the impeachment since he believes Trump did not commit a crime nor "even do anything improper."

"There is no case," Kurzeja said, "They (the Democrats) are harming America."

The Trump supporter said he felt bad at Washington's politics, calling it "a swamp, figuratively and literally."

The political atmosphere in the country "is going to get worse before it gets better," he said. "We are coming into an election year. Election years are usually pretty frenzy. Because of the impeachment, it's going to be more frenzy than most."

"The level of partisanship and polarization that we're seeing in Congress now is quite large, even compared to the Clinton impeachment in the 1990s," Molly Reynolds, a senior fellow in Governance Studies at Brookings, told a seminar on Tuesday.

Among the US public, support for impeaching Trump stands at 45 percent while opposition stands at 47 percent, almost evenly, according to a new CNN poll released one day before the full House impeachment debate and vote.

House Democrats have accused Trump of abusing his office by pressuring Ukraine to pursue investigations into political opponent that could benefit his reelection campaign. The White House has refused to cooperate in the impeachment inquiry, accusing Democrats of an unfair process that aims to overturn the results of the 2016 election.

Under the US constitution, the House has the sole power of impeachment while the Senate has the sole power to try all impeachments. Conviction can only happen in the Senate and requires at least two-thirds of its members, or 67 senators, to vote in favor after a trial.

Trump is widely expected to be acquitted if the articles of impeachment move to a trial in the Senate next year.