President Donald Trump's lawyers urged the US Senate on Tuesday to reject the charges against him, closing their impeachment defense by accusing the Democrats of placing him on trial for political reasons."What they are asking you to do is to throw out a successful president on the eve of an election with no basis and in violation of the constitution," Trump's lead defense lawyer Pat Cipollone said."The American people are entitled to choose their president," he said. "We urge the Senate to reject these articles of impeachment."Trump's lawyers wound up their three-day defense of Trump, who is charged with abuse of power and obstruction of Congress, arguing that the allegations against him are too minor and too thinly-sourced to justify convicting and removing the US leader."If partisan impeachment is now the rule of the day... future presidents, Democrats Republicans, will be paralyzed the moment they are elected," said Jay Sekulow, another Trump lawyer."The bar for impeachment cannot be set this low."But the trial faced fresh controversy as Democrats demanded that Trump's former national security advisor John Bolton be called as a witness.A draft of a forthcoming book by Bolton, according to The New York Times, says that Trump told him in August that security aid to Ukraine had been held up to pressure the country to announce investigations into Trump's possible 2020 reelection rival Joe Biden - the allegation at the heart of the impeachment case."If you don't believe the newspaper report, call the witnesses," said Senate Democratic leader Chuck Schumer."Let the chips fall where they may. Get the truth," he said.