WASHINGTON — House Democrats launched into marathon arguments in President Donald Trump’s impeachment trial Wednesday, appealing to skeptical Republican senators to join them in voting to oust Trump from office to “protect our democracy.”

Trump’s lawyers sat by, waiting their turn, as t he president blasted the proceedings from afar, threatening jokingly to face off with the Democrats by coming to “sit right in the front row and stare at their corrupt faces.”

The challenge before the House managers is clear. Democrats have 24 hours over three days to prosecute the charges against Trump, trying to win over not just fidgety senators sitting silently in the chamber but an American public, deeply divided over the president and his impeachment in an election year.

Rep. Adam Schiff, chairman of the House Intelligence Committee, outlined what the Democrats contend was the president’s “corrupt scheme” to abuse his presidential power and then obstruct Congress’ investigation. He then called on senators not to be “cynical” about politics, but to draw on the intent of the nation’s Founding Fathers who provided the remedy of impeachment.

“Over the coming days, we will present to you–and to the American people–the extensive evidence collected during the House’s impeachment inquiry into the president’s abuse of power,” said Schiff standing before the Senate. “You will hear their testimony at the same time as the American people. That is, if you will allow it.”

Most senators sat at their desks throughout, as the rules stipulate, though some stretched their legs, standing behind the desks or against the back wall of the chamber, passing the time. Visitors watched from the galleries, one briefly interrupting in protest.

The proceedings are unfolding at the start of an election year, and there are few signs that Republicans are interested in calling more witnesses or going beyond a fast-track assessment that is likely to bring a quick vote on charges related to Trump’s dealings with Ukraine.

The trial marks just the third time the Senate has weighed whether an American president should be removed from office. Democrats argue Trump abused his office by asking Ukraine to investigate political rival Joe Biden while withholding crucial military aid, and also obstructed Congress by refusing to turn over documents or allow officials to testify in the House probe. Republicans have defended Trump’s actions and cast the process as a politically motivated effort to weaken the president in the midst of his reelection campaign.

A new poll from The Associated Press-NORC Center for Public Affairs Research shows the public is slightly more likely to say the Senate should convict and remove Trump from office than to say it should not, 45% to 40%. But a sizable percentage, 14%, say they don’t know enough to have an opinion.

One question there’s wide agreement on: Trump should allow top aides to appear as witnesses at the trial. About 7 in 10 said so, including majorities of Republicans and Democrats, according to the poll.

The strategy of more witnesses, though, seems all but settled. Wrangling over rules for the trial stretched past midnight Tuesday night, with Republicans shooting down one-by-one Democratic efforts to get Trump aides including former national security adviser John Bolton, Secretary of State Mike Pompeo, and acting chief of staff Mick Mulvaney, to testify.