By Richard Cowan and David Morgan

WASHINGTON (Reuters) – The lead Democratic prosecutor accused President Donald Trump at his impeachment trial in the U.S. Senate on Wednesday of setting up a corrupt scheme to pressure Ukraine to help him win re-election this coming November.

Trump sounded a defiant note, telling reporters in Switzerland that Democrats did not have enough evidence against him.

In the opening argument for the prosecution, Representative Adam Schiff said Trump had pushed Ukrainian President Volodymyr Zelenskiy to investigate former Vice President Joe Biden and his son on unsubstantiated corruption charges last year.

In his dealings with Ukraine, Trump solicited foreign interference to improve his chances in this year’s U.S. presidential election, Schiff said, laying out the main Democratic argument for why Trump abused his power and should be found guilty.

“To implement this corrupt scheme President Trump pressured the president of Ukraine to publicly announce investigations into two discredited allegations that would benefit President Trump’s 2020 presidential campaign,” Schiff said.

Democrats argue that Trump was trying to find dirt on Biden, a leading contender for the Democratic presidential nomination, and his son Hunter who had served on the board of a Ukrainian gas company, to help the Republican president win a second term.

Trump denies any wrongdoing and his fellow Republicans in the Senate say his behavior did not fit the description of “high crimes and misdemeanors” outlined in the U.S. Constitution as a reason to oust a U.S. president.

Trump is almost certain to be acquitted by the Republican-controlled 100-member Senate, where a two-thirds majority is needed to remove him from office. But the trial’s effect on Trump’s November re-election bid is unclear.

The case against him is focused on a July 25 telephone call in which he asked Zelenskiy to open a corruption investigation into the Bidens as well as a discredited theory that Ukraine, not Russia, meddled in the 2016 U.S. election.

“Nothing could be more dangerous to a democracy than a commander in chief who believed that he could operate with impunity, free from accountability. Nothing, that is, except a Congress that is willing to let it be so,” said Schiff, who is leading the prosecution team of Democratic “managers” from the 435-seat House of Representatives.

Democrats have up to three days to make their case. Trump’s defense team will have three days after that for rebuttal in a trial that could potentially conclude next week.

It is the third presidential impeachment trial in U.S. history. The opening days have been dominated by arguments over Democratic requests for more witnesses and records.

The Trump administration has not complied with subpoenas for documents and has urged officials like former national security adviser John Bolton and Secretary of State Mike Pompeo not to participate in the impeachment investigation.

In Davos, Switzerland, Trump told reporters at the World Economic Forum that he was happy with the way the trial was going.

“I thought our team did a very good job. But honestly, we have all the material. They don’t have the material,” Trump said.

(Reporting by Richard Cowan and David Morgan; Additional reporting by Doina Chiacu and Susan Heavey; Writing by Alistair Bell; Editing by Andy Sullivan and Howard Goller)