WASHINGTON — Democrats may want to be careful what they wish for in demanding witnesses in President Donald Trump's Senate impeachment trial.

That's the warning some party strategists are sending as House Speaker Nancy Pelosi, D-Calif., prepares to send two articles of impeachment and a roster of House prosecutors to Senate Majority Leader Mitch McConnell, R-Ky., later this week.

"Given where things stand right now, there's only one smart solution: Get out of this as quickly as possible," said Democratic strategist Chris Kofinis, former chief of staff for Sen. Joe Manchin of West Virginia.

The tension lies not in the facts of the case but in the politics of convincing voters that Trump is unfit for the presidency before November's election. Democrats are certain that the president violated his duty to the country and equally sure that there's zero chance that the necessary two-thirds of the Senate — a share that would require 20 or more Republicans — will vote to remove him from office.

The question for Democrats is whether the value of witnesses outweighs the risks.

The upside is the possibility that figures close to Trump, from acting White House chief of staff Mick Mulvaney to former national security adviser John Bolton, could produce new evidence that would harm Trump in the eyes of the public.

But the perils include testimony adverse to Democrats' case, losing the opportunity to cast Senate Republicans in tough re-election campaigns as a cover-up squad for the president, and giving Trump a bigger platform to continue the guilt-by-aspersion campaign against former Vice President Joe Biden that triggered his impeachment in the first place.

Even if Trump advisers testify and Biden doesn't, a fight would give Trump a measure of what he wants — more attention on Biden and his son, Hunter Biden — and it's possible that witnesses called by Democrats would find ways, among them asserting executive privilege, to ensure that any testimony helps rather than harms the president.

"Anyone who thinks Bolton's going to turn on Trump is on drugs," Kofinis said.

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In an ideal world for Democrats, a string of Trump's lieutenants would swear oaths to tell the truth and offer a litany of new details that would damn the president in the eyes of Republican senators and persuadable voters. Calls for the Bidens to testify would evaporate into the darkened cloud hanging over Trump's presidency.

That prospect — that there's more to be learned, none of it good for Trump — is the reason many Democrats are eager to press forward on securing testimony from the president's inner circle.

Republicans, who control the process in the Senate, appear to be moving forward on two tracks: McConnell says he has garnered the votes necessary to begin the trial without guaranteeing testimony, while Sen. Susan Collins, R-Maine, told NBC News last week that she is talking with GOP colleagues about a possible plan to vote to add witnesses later.

"I am hopeful that we can reach an agreement on how to proceed with the trial that will allow the opportunity for witnesses for both the House managers and the president's counsel if they choose to do so," she said. "It is important that both sides be treated fairly."

Collins, who is one of a handful of Republicans in hotly contested re-election campaigns, has a close relationship with McConnell, and her nod to witnesses important to the president's attorneys could easily be read as a reference to the Bidens. The theory of Trump's defense rests in part on the idea that pursuing investigations into the Bidens was less about securing his re-election at the expense of national security interests than it was about his international anti-corruption efforts.

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Some Democrats see raising the prospect of calling Joe Biden or his son to testify as a threat that the president and his allies can't follow through on. The reasoning is that at least a small set of Republicans will decide that it would make a mockery of the Senate to force the testimony of figures who can't shed light on actions by the president that led to his impeachment.

"Democrats should not be cowed into dropping their demand for more witnesses," said Jim Manley, a top aide to Harry Reid, D-Nev., when Reid was the Senate majority leader. "There's not a snowball's chance in hell that there will be the votes necessary to call Hunter Biden, Joe Biden or anyone else, for that matter, who is not connected to Trump's abuse of power."

Manley acknowledged that Republicans aren't going to vote Trump out of office, but he said it's important for the public to hear as much as possible about what the president did.

"Even if Democrats got every witness they demanded, it is impossible for me to ever think that there will be the 67 votes needed to convict," he said. "They should make the best case they can and leave it to the American people to do the right thing and defeat Trump at the ballot box in November."

Republicans facing tough re-election bids have to be careful that voters in their own states don't blame them for failing to do their jobs well — by giving the president either too much cover or too little.

Ron Bonjean, a former Senate Republican leadership aide, said he doesn't see a majority of senators having the appetite for a sprawling witness list.

"It's going to come down to whether or not moderate Republicans join Democrats at calling witnesses," he said. "This means that the trial will most likely either proceed without witnesses or have only a few to hear from during the proceedings."

Witnesses could provide more detail, but it's unlikely that they would change the basic narrative.

Of course, it's possible that Democratic lawmakers are pressing for witnesses simply to set up the argument that Trump and Senate Republicans are covering up misconduct.

"If McConnell succeeds in making this trial a trial without witnesses, that's not a fair trial — that's a sham," House Intelligence Committee Chairman Adam Schiff, D-Calif., said Sunday on CBS' "Face the Nation."

But Schiff hasn't subpoenaed Bolton.

"It's certainly something that we are considering," he said.