Washington (CNN) The Senate Intelligence Committee remains deeply divided over whether there is evidence of collusion between Donald Trump's campaign and Russia after a year-long investigation, the latest sign that Congress is unlikely to find consensus over a key question surrounding the 2016 elections.

The committee has tried for the past year to showcase bipartisanship in its investigation, taking pride that it has yet to devolve into public partisan mudslinging like its counterpart in the House. But by taking the high ground, the committee has so far punted on making any determination about collusion.

Now, senators now find themselves facing the same partisan pitfalls as the House and the rest of Washington over whether there was any collusion and when it should release a report that would have broad ramifications for Trump and the November midterms.

Republicans on the panel maintain they've seen no evidence of collusion, while Democrats say it's clear that the Russians had found willing partners in the Trump campaign to sway the 2016 race.

"There was clearly an intent to collude," said Oregon Democratic Sen. Ron Wyden.

Asked if he believes there's evidence to support the notion of collusion, GOP Sen. Roy Blunt said: "Not that I've seen."

Republican Sen. Susan Collins of Maine agreed.

"Our investigation is not complete, but to this date and time I have not," Collins said when asked if she'd seen evidence of collusion.

Intelligence Chairman Richard Burr, a North Carolina Republican, said that the committee has "a handful" of witnesses remaining to interview. He was hopeful the interviews could be completed by June and the report itself could be done by Labor Day -- but it's unclear if the panel will be able to release an unclassified report before the midterms.

Added to the complications: midterm politics and special counsel Robert Mueller's investigation. Some on the panel, like Collins, resist the idea of issuing a report on collusion in the run-up to the midterm elections when control of Congress will be at stake, while others are skeptical about concluding their probe while Mueller appears to be charging ahead.

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"No, no," said California Democratic Sen. Dianne Feinstein, said when asked if the panel's report on collusion would be as definitive as Mueller's probe. "Look what he's done with the indictment," she said, referring to the 13 Russians charged by the special counsel for allegedly seeking to meddle in the 2016 race. "So I think they have a level of professionalism and a level of law behind them that we don't."

Sen. Joe Manchin, a Democrat facing a tough re-election battle in West Virginia, said the ultimate question about whether Trump associates colluded with the Russians will be decided by Mueller. "I really think that's where Mueller will prove that case. ... I think he's done deeper dives than we did," Manchin said, citing "tools" that the committee doesn't have.

How the committee ultimately deals with the matter will be a major test for the two leaders of the panel, Burr and Vice Chairman Mark Warner, a Democrat. Burr, in particular, has managed to distance himself from the controversy engulfing House Intelligence Chairman Devin Nunes, who has taken a series of steps that have given the White House ammunition to fight back against the investigations, from his "memo" alleging surveillance abuses to a GOP committee that stated the panel found no evidence of collusion.

Burr cannot hold out forever -- he at some point will have to wade into the issue of collusion that could either help Trump's case -- or put him in the crosshairs of the President of his own party.

In recent interviews, Burr has expressed skepticism that there was collusion, but he has been careful not to make a judgment yet.

"I'm going to wait until we have all the facts before I make a determination," Burr said.

Yet Burr has resisted Democratic demands to bring Trump associates back for a second round of interviews to sit down for questioning by senators after their initial meetings with Senate staff. Senators have not participated in the vast majority of interviews with witnesses so far, leaving it to the staff of the panel, which Burr has argued is how the committee has traditionally conducted major investigations.

Indeed, Burr has backtracked on a pledge he gave to bring back Trump's personal lawyer Michael Cohen, who met privately with committee staff last year.

"Not that I know of right now," Burr said when asked last month if he had more questions for Cohen.

Moreover, Burr has been uneager to dig into other areas at the request of Democrats like Wyden, who say the panel needs to fully investigate Trump's finances to learn about the extent of the Russia connections.

"I am not at all satisfied on where the committee is on the follow-the-money issue, and if anything, the case for following the money is stronger today than it was 60 days ago," Wyden said last week, citing reports about Cohen receiving payments for a firm with ties to a Russian oligarch.

Warner, however, has suggested that the issue about potential money laundering was better suited for Mueller to investigate -- not the Senate panel. And Warner has been cautious about asserting that the panel has evidence to make a definitive statement on collusion.

"We're going through this on a methodical basis and will follow the facts," said Warner, who would not predict the probe would conclude before November.

Others are more forceful in their beliefs on collusion.

Sen. Jim Risch, an Idaho Republican, made clear he sees no evidence of collusion and doesn't expect any will emerge, seizing on comments last year from Feinstein that she hadn't seen any evidence that the campaign received "dirt" on Hillary Clinton from the Russians.

"I've been ready a long time now. I'm so ready you can't believe it," Risch said of the end of the investigation. "I've looked at thousands and thousands of pages and reviewed the transcripts. I'm not at liberty to disclose what my conclusion is, but Dianne Feinstein said some time ago she saw no evidence of collusion, and Dianne is a really good friend of mind - and sometimes she gets things exactly right."

Feinstein pushed back.

"Define collusion," Feinstein said when asked if she believed there was evidence showing collusion. "Were there meetings to discuss things? We know there were. Is that collusion? So, I think the definitive (investigation) is the Mueller probe."

A committee source said senators may not agree about whether Trump is tied to any potential collusion. But the source said that a majority of senators on the panel are on the same page when it comes to the facts surrounding problematic contacts that members of Trump's team had with Russians during the campaign.

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Interim reports

As the committee's investigation crossed the one-year mark, Burr and Warner began releasing portions of their investigation that had been completed in March -- on issues separate from collusion where the panel could achieve bipartisan consensus.

The senators have put out an unclassified report and recommendations tied to election security and finished their examination of the US Intelligence Community's January 2017 assessment, agreeing with the conclusion that Russian President Vladimir Putin was trying to help Trump in 2016 -- a finding that was at odds with Republicans on the House Intelligence Committee.

Burr and Warner are planning two more interim reports, one on the Obama administration's response to the Russian meddling, and another on the use of social media in the election.

Then once those are done, the committee will be left to try to tackle the collusion question.

The committee has interviewed more than 100 witnesses and reviewed hundreds of thousands of pages of documents related to the probe that's been underway since January 2017.

And while the committee's senators largely said they should operate separately from Mueller, the special counsel investigation has already proven the ability to uncover information that Congress does not have, which could potentially change the trajectory of the Senate probe should they wait for more of Mueller's findings.

Over the course of the various Russia investigations, numerous contacts between Trump's team and Russians have been uncovered, including the 2016 Trump Tower meeting between Donald Trump Jr. and Russian operatives, as well as Trump foreign policy campaign adviser George Papadopoulos' 2016 meeting with a London professor who also was offering damaging information on Clinton that came from the Russians.

"I think what's clear is there was a set of relationships and a friendliness inside this campaign with high-level Russian operatives that we've really never an analog for in our country's history," said Sen. Martin Heinrich, a New Mexico Democrat. "I'm not going to speak prematurely to the outcome of the investigation but I think that alone should be shocking to the American people."

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Finished by Labor Day?

Burr has suggested the report can be done by Labor Day.

"This gives us the month of August in all likelihood to wrap up our investigation. And for staff to work intensely while we're out of here not getting in their hair," Burr said. "We could be in a situation where members could look at that and digest it over the beginning of September."

Burr, however, has previously predicted the investigation could have concluded by the end of 2017 and early into 2018, deadlines that have come and gone while the committee continues to quietly interview witnesses. And it's not clear, even if the committee completed its investigation by September, whether it would be able to release an unclassified report before the midterms.

But the schedule could create a dilemma for Burr.

Some, liked Democratic Sen. Kamala Harris, argue that the election should have no bearing on when the committee puts out its final document.

"I think that it should run its natural course," Harris said. "Certainly it shouldn't be motivated by any election or politics at all."

Yet others are skeptical about taking such a step in the heat of the midterms, saying the conclusion will be viewed skeptically by the public.

Manchin argued that anything issued right before the elections risks being viewed as "politically motivated" that is "not going to help us come to the conclusion we have confidence and faith in."

Collins praised Burr and Warner for their handling of the investigation so far, but she said she had concerns about the report coming out in the heat of the campaign season. "I think that it should not be right before the midterms," she said.