(Adds more details from documents, background; link to Democratic brief)
By Patricia Zengerle and Steve Holland
WASHINGTON/PALM BEACH, Fla., Jan 18 (Reuters) - The Democratic U.S. lawmakers leading the impeachment case against Republican President Donald Trump said on Saturday the president must be removed from office to protect national security and preserve the country's system of government.
In a brief filed ahead of a Saturday deadline, the lawmakers laid out their arguments supporting charges of abuse of power and obstruction of Congress against the president.
"The Senate should convict and remove President Trump to avoid serious and long term damage to our democratic values and the nation's security," the lawmakers said, for the first time formally calling for the Senate to convict the president and remove him from office.
"The case against the president of the United States is simple, the facts are indisputable, and the evidence is overwhelming," they said.
Trump's legal team issued a resounding rejection of the House of Representatives' impeachment, calling the charges a "dangerous attack on the right of the American people to freely choose their president."
"This is a brazen and unlawful attempt to overturn the results of the 2016 election and interfere with the 2020 election -- now just months away," they argued in a six-page document released on Saturday.
It was the first time Trump had formally addressed the merits of the two articles of impeachment - abuse of power and obstruction of Congress - that the Democratic-led House approved late last year.
The two articles, aimed at ousting Trump from office, form the basis of a trial that will begin in earnest on Tuesday in the Republican-controlled Senate.
Trump and Democratic lawmakers offered dueling arguments about the politically polarizing impeachment case involving Trump's attempt to persuade Ukraine President Volodymyr Zelenskiy to investigate Democratic rival Joe Biden last year.
"President Trump categorically and unequivocally denies each and every allegation in both articles of impeachment," the Trump lawyers' document said. (For full document see https://www.whitehouse.gov/wp-content/uploads/2020/01/Answer-of-President-Donald-J.-Trump.pdf)
As well as the charge of abuse of office for pressuring Ukraine to investigate Biden and his son Hunter Biden, Trump is also accused of obstructing Congress in its investigation into his conduct.
"An acquittal would also provide license to President Trump and his successors to use taxpayer dollars for personal political ends," the Democratic lawmakers' brief said. (For full document see https://intelligence.house.gov/uploadedfiles/in_re_president_trump_house_impeachment_trial_brief_and_sof_1.18.20.pdf)
Trump has denied wrongdoing and has accused Democrats of a partisan-driven effort to undo his 2016 election victory.
The Senate trial is unlikely to lead to Trump's ouster, as no Republican senators have voiced support for doing so.
Trump, at his Mar-a-Lago club in Palm Beach, Florida, for the weekend, played a round of golf on Saturday.
The Trump lawyers, in their document, argued that Trump acted at all times with full constitutional legal authority, said one of three sources close to Trump's legal team who briefed reporters on a conference call on Saturday. "We will take the facts head on and we believe that the facts will prove, and have proven, that the president did absolutely nothing wrong," the source said. (Reporting by Steve Holland and Patricia Zengerle Editing by Paul Simao and Chizu Nomiyama)
Our Standards: The Thomson Reuters Trust Principles.