Senator Amy Klobuchar of Minnesota, who sits on the Senate Judiciary Committee and is a candidate for the Democratic presidential nomination for 2020, said Monday that Congress cannot decide whether or not to pursue impeachment of President Donald Trump without seeing the full Mueller report.

On Sunday, Attorney General William Barr issued a four-page summary of Special Counsel Robert Mueller's findings. While the letter quoted Mueller's report as stating that Mr. Trump was not exonerated on the matter of obstruction of justice and that there was "evidence on both sides of the question," Barr determined that there was insufficient evidence to indict.

The Barr summary also stated that while Mueller's office "did not find that the Trump campaign, or anyone associated with it, conspired or coordinated with the Russian government in these efforts, despite multiple offers from Russian-affiliated individuals to assist the Trump campaign."

Democrats in Congress are demanding that the full Mueller report be released to see the underlying evidence, and there are calls to subpoena Barr and Mueller to testify.

Klobuchar told "CBS This Morning" it would be up to Democrats in the House whether to consider impeachment, "but they cannot make the decision until we have the entire report. Four hundred and twenty members of the House voted that that report should be public, and that hasn't happened.

"This is simply a four-page letter from the president's attorney general that summarizes what happened and leaves open a lot of questions, like saying that the report sets out evidence 'on both sides of the question' and, 'it does not exonerate him,' meaning the president. So to me, if I'm in the House looking at that question, I want to see the whole report, and certainly the public wants to see the report. Nearly 90% of the public has said that they want to see the report."

When asked by co-host Bianna Golodryga if Democrats were in a difficult position going forward, pursuing investigations of the president following Barr's letter, Klobuchar said that Americans she has spoken with on the campaign trail are concerned by what happened in the 2016 election.

"Americans understand how important the Constitution is to garner individual freedoms," she said. "I think the point here is they want to see what happened and the most important reason they ask it is because they want to have an election free of an invasion by a foreign power. And that shouldn't be forgotten here.

"What this four-page letter does among many things is it makes clear that that happened. It happened in two ways: Hacking into our election systems, as well as putting out misinformation. And I certainly want to see all of that information in the underlying Mueller report because it dictates what we should do going forward. I think we should have backup paper ballots in every state in this country. There could well be another invasion and hacking into our equipment. Americans don't want to see that."

Co-host John Dickerson asked Klobuchar, "You're a former prosecutor and you oversee the attorney general as a member of the Judiciary Committee. What do you make of the attorney general's ruling that you can't have obstruction if there's not an underlying crime of collusion?"

"I don't see it quite that way," she replied. "But again, without seeing the facts, without seeing the entire report, it is very hard to assess any of this. And Barr – during his [confirmation] hearing and now as attorney general – has pledged that he wants to make everything he can public. And we're going to call him on that."

CBS News will present a one-hour special report, "The Mueller Report: A Turning Point," beginning at 10 p.m. ET/PT.