WASHINGTON (REUTERS) - A bitterly divided United States House of Representatives engaged in an impeachment debate before historic votes on two charges accusing President Donald Trump of abusing his power and obstructing Congress.

Here are some highlights from the contentious back-and-forth between Democratic and Republican lawmakers ahead of the vote:

A NATIONAL CIVICS LESSON

Speaker Nancy Pelosi opened six hours of impeachment debate in the Democratic-controlled House by saying: "Today is a national civics lesson, though a sad one.

"I solemnly and sadly open the debate on impeachment of the President of the United States. If we do not act now, we would be derelict in our duty," the Democratic leader said, calling the US Congress the "custodians of the Constitution".

INEVITABILITY

Representative Doug Collins, the top Republican on the Judiciary Committee, said Democrats had begun plotting Mr Trump's impeachment even before his dealings with Ukraine, which form the core of the impeachment case, became public in September.

"To Democrats, it's politics, not facts, that matter," Mr Collins said on the House floor.

CANNOT WAIT

House Judiciary Committee chairman Jerrold Nadler said the impeachment drive was not an attempt to overturn Mr Trump's 2016 victory. But he said Mr Trump's actions threatened the integrity of the November 2020 presidential and congressional elections.

"Congress cannot wait until the next election to address this conduct," he said.

There are currently 15 candidates vying for the Democratic Party's nomination to take on Mr Trump in November 2020. Five of them are US senators who will act as jurors in the impeachment trial.

PATRIOTS SHALL PREVAIL

Republican Representative Clay Higgins, who last year beat out six opponents in Louisiana to win a second term with Mr Trump's endorsement, warned that "America is being severely injured by this betrayal", referring to the impeachment proceedings.

"We will never surrender our nation to career establishment DC politicians and bureaucrats. Our republic shall survive this threat from within. American patriots shall prevail," Mr Higgins said.

CLEAR AND PRESENT DANGER

Democratic Representative Veronica Escobar said the impeachment represented "a great tragedy and a moment of truth" for Mr Trump.

"We have witnessed the president of the United States abuse his public office for personal political gain and invite foreign governments to interfere in our elections," Ms Escobar said, adding that the evidence showed he was a "clear and present danger" to fair elections and national security.

INFAMY

Republican Representative Mike Kelly compared the impeachment vote to Japan's military attack on the US naval base at Pearl Harbor, in Hawaii, on Dec 7, 1941 - a date that President Franklin Roosevelt said would "live in infamy".

"Today, Dec 18, 2019, is another date that will live in infamy," Mr Kelly said.

SHAM TRIAL

Georgia Republican Representative Barry Loudermilk said Jesus was treated more fairly ahead of his crucifixion than Democrats have treated Mr Trump during the impeachment proceedings.

"During that sham trial, Pontius Pilate afforded more rights to Jesus than Democrats have afforded this president in this process," Mr Loudermilk said.