WASHINGTON — With opening arguments wrapped up in President Donald Trump’s impeachment trial, the next phase begins. For the next two days, senators get to ask questions of both legal teams. During that time, people will be looking for signs of whether enough Republicans will cross the aisle and agree to bring in witnesses -- particularly former national security adviser John Bolton.

On Wednesday and Thursday, senators will submit questions on pieces of paper to be read out loud by Chief Justice John Roberts. The questions will be addressed to House managers or Trump's defense team. According to the Associated Press, the senators cannot ask the questions themselves and cannot respond to the answers. This way, the senators are forced to remain silent.

The question can only be addressed to either the House team or the Trump team, not both. 

Each question-and-answer day will last eight hours, with a break coming after every 10 to 12 questions. AP reports Democrats and Republicans will take turns asking questions. Roberts will urge each team of lawyers to limit their answers to five minutes.

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McConnell doesn't have votes to prevent witnesses, yet

Trump's defense team rested Tuesday with a plea to end the trial now, but Senate Majority Leader Mitch McConnell privately told senators he doesn't yet have the votes to brush back Democratic demands for witnesses.

Those demands gained steam with John Bolton asserting in a forthcoming book that Trump tied military aid from Ukraine to investigations into Democratic rival Joe Biden. That claim directly undercuts a claim by Trump's team that the holdup of aid was not tied to electoral politics.

A letter from Bolton's attorney indicates the White House received a copy of Bolton's manuscript for about a month, but the details of its contents were first made public last weekend.

Trump was impeached on charges that he abused his power by holding up the military aid as leverage in exchange for a publicly-announced investigation into the Bidens. Democrats also impeached Trump for what they say were his efforts to block the House investigation into the matter.

Trump tweeted Wednesday night, asking why Bolton had not brought up his concerns previously.

"Why didn’t John Bolton complain about this 'nonsense' a long time ago, when he was very publicly terminated. He said, not that it matters, NOTHING!" Trump tweeted.

Bolton received some public backing by former White House Chief of Staff John Kelly. He told an audience in Sarasota, Florida, Tuesday that he believes the former national security adviser.

Some Republicans have floated the idea of trading witnesses -- allowing Republicans to call someone such as Joe Biden or his son, Hunter, in exchange for allowing Democratic witnesses. Democrats have scoffed at the proposal. But, Republicans hold the majority in the Senate. They could call their own witnesses without giving the Democrats any deal.

If no witnesses are called, the trial could wrap up this weekend. But if witnesses are allowed, it would spread out the trial for an undetermined amount of time, taking it into the Democratic primary season as well as next Tuesday's State of the Union address.

Associated Press writers Alan Fram, Mary Clare Jalonick, Andrew Taylor, Matthew Daly, Laurie Kellman and Padmananda Rama contributed to this report.