In this July 10, 2019, file photo, Sen. Doug Jones, D-Alabama, arrives for a closed door meeting for Senators on election security on Capitol Hill in Washington. Credit: Andrew Harnik | AP

Sen. Doug Jones, D-Alabama, who won a special election victory in 2017 and faces a difficult re-election campaign next year, said Sunday that he remains undecided on whether President Donald Trump should be removed from office.

Jones — a former prosecutor and moderate Democrat representing a deeply conservative state that overwhelmingly backed Trump’s presidential campaign in 2016 — said he is keeping his mind open ahead of the pending Senate trial, following the House’s vote to impeach the president last week.

“Quite frankly, I didn’t sit in front of the TV set the entire time the last two or three months. I’ve been trying to read this. I’m trying to see if the dots get connected,” Jones said in an interview on ABC’s “This Week.” “If that is the case, then I think it’s a serious matter. I think it’s an impeachable matter.”

But, Jones added, “If those dots aren’t connected and there are other explanations that I think are consistent with innocence, I will go that way, too. I have got to make sure that — what I really want to see, though, is to fill in the gaps. … I would like to see a full and complete picture.”

At the start of the impeachment hearing, the senators will take an oath to provide “impartial justice.” As a result, most senate Democrats have declined to say whether they’ll vote to remove Trump from office, and have chastised their Senate Republican colleagues for publicly promising to work to acquit the president. But Jones’ comments on “This Week” were unusually equivocal, signaling the tricky political tightrope Jones must walk.

Jones and other Democrats who represent states won by Trump, such as Sen. Joe Manchin III, D-West Virginia, and Sen. Gary Peters, D-Michigan, are seen by top Republican strategists as possible swing votes in a Senate trial.

But Jones is considered by party leaders to be the most vulnerable Senate Democrat ahead of the 2020 campaign season, because Trump defeated Democratic candidate Hillary Clinton by 28 percentage points in Alabama.

Republicans who are being monitored ahead of a Senate trial include Sens. Susan Collins of Maine, Lisa Murkowski of Alaska and Mitt Romney of Utah, according to two GOP officials who were not authorized to speak publicly.

On Sunday, Jones also called on Senate Majority Leader Mitch McConnell, R-Kentucky, to work with Trump to “have his people come and testify and deliver documents.”

A day after the House voted to impeach Trump, House Speaker Nancy Pelosi, D-California, announced she would refrain from sending the articles of impeachment to the Senate until McConnell sets rules for the trial that are accepted by Senate Democrats.

The House voted Thursday to adjourn for the holidays until Jan. 7, throwing into doubt when the Senate might be able to begin its trial, potentially pushing it further into an election year and threatening to deny Trump the satisfaction of a swift acquittal.

Pelosi’s maneuver underscored her eagerness to maintain control over the process rather than turning over the reins to McConnell. It was also part of a Democratic effort to pressure Senate Republicans to allow testimony from key Trump administration officials who had defied subpoenas during the House’s inquiry.

“We ask, is the president’s case so weak that none of the president’s men can defend him under oath?” Senate Minority Leader Charles Schumer, D-New York, said last week.

Trump, McConnell and other Republicans cried foul, accusing Pelosi and the Democrats of presenting a weak case against the president for abuse of office and obstruction of Congress and effectively withholding those charges from Senate scrutiny.

“She’s not going to hold these forever,” Jones said Sunday. “We’re going to see these relatively soon, but I don’t think it’s unfair to ask, ‘What are the rules that we’re playing by, when we go and we get this over here?’ “

The Republican primary race to challenge Jones is crowded. Former attorney general and former senator Jeff Sessions has launched a comeback bid, and Rep. Bradley Byrne, R-Alabama, is also running, as are former Auburn University football coach Tommy Tuberville and Roy Moore, among others.

Sessions, whose turbulent two-year stint in the administration ended in dramatic fashion when he was forced out by Trump in November 2018, entered the contest last month with strong name recognition and deep institutional ties in the state and elsewhere. He held the seat for two decades before he became Trump’s first U.S. attorney general.

Moore was the party’s Senate candidate in 2017 amid allegations of sexual misconduct with teenage girls in the 1970s. Moore has acknowledged interactions with the women but denied any sexual contact.

Jones narrowly beat Moore two years ago, lifted by a backlash against Moore by not only Democrats but many Republicans in the conservative state.

Washington Post writer Seung Min Kim contributed to this report.