Clint Watts, a senior fellow at George Washington University's Center for Cyber and Homeland Security, said Russians put out some negative information on Trump "but it was 90 percent positive".
Cohen-Watnick is among about a dozen White House officials who would have access to the types of classified information Nunes says he viewed, according to current and former US officials.
Burr said Russia's election interference methods had "already been tried in Montenegro and the Netherlands".
"I'm a little bit lost as to what our interests are or how they're coalescing", Watts said.
Russian Federation is "actively involved" in the French and German elections scheduled for later this year, Senate Intelligence Committee Chairman Richard Burr warned Wednesday.
"It's exclusively based on what they want to achieve in their own landscape, whatever the Russian foreign policy objectives are", he said.
Burr has said that so far, the Senate committee has requested 20 individuals to be interviewed.
What was mostly lacking were the partisan shots from Democrats and Republicans that highlighted the House's first public hearing last Monday - where Democrats focused nearly exclusively on trying to dig out information on Trump aides, and Republicans pushed largely to try to identify who released information to the press, at one point even suggesting it may have been President Barack Obama himself.
Burr and Warner have pledged cooperation with each other on the committee's probe of Russia's influence during the campaign, distancing themselves from the fractured House intelligence committee's investigation that has been fraught with partisanship.
"The Kremlin made effective use of its hacking skills to steal and weaponize information and engage in a coordinated effort to damage a particular candidate and to undermine public confidence in our democratic process", U.S. Senator Mark Warner (D-Va.) said.
He said that the intelligence panel's investigation should look at the Trump Organization and its partnerships. He most certainly doesn't want to ruin his legacy in his third term in the way House intell chair Devin Nunes has.
In the tweet, Trump said his former national security adviser, Michael Flynn, should seek immunity in exchange for his testimony to federal and congressional investigators in their probe.
During a news conference, Burr identified just one of the witnesses: President Donald Trump's son-in-law, Jared Kushner.
"I think it's reached a new level where it requires a select committee", McCain said on Fox News' "America's Newsroom" television program.
This post will be updated as the Senate Intelligence Committee hearing continues.
At the hearing, lawmakers warned of the danger that Russian Federation could interfere in elections in France and Germany this year and in future US campaigns.
Meanwhile, Burr promised at the start of Thursday's Senate hearing that his panel would hold more public hearing as they continued their investigation.
Warner's follow Democrat Senator Ron Wyden also urged the Senate to "follow the money" on Russia, adding real estate deals and money-laundering might mean the "Russian government may be only a step or two away" from American institutions.