1. SOUNDBITE: (English) Sen. Richard Blumenthal, (D) Connecticut:
"The president is coming close to actual committing the crime of obstruction of justice, if not crossing that line already and these tweets, adding to each other, amount to evidence of criminal intent. There is now, right now, a clearly credible case of obstruction of justice against the President of the United States. That case is based on tweets, on other actions and conversations together, all of these actions, including the most recent tweet are a powerful mosaic. There may be still pieces that are needed, but it's awful close."
2. SOUNDBITE: (English) Sen. Ben Cardin, (D) Maryland:
"The president's comments I find to be extremely regrettable. It interferes with the separation of powers and that is the investigative powers -- no one's above the law. Attorney General Sessions did the right thing in recusing himself and that investigation should be left to find its conclusions without interference from the president or Congress."
3. SOUNDBITE: (English) Sen. Sherrod Brown, (D) Ohio:
"I know that this president clearly feels like the walls are are coming in on him, are collapsing in on him, with the with the tweets with his attacks against everybody. He attacks pretty much everybody but Putin. He attacks people in his own party, he attacks people that are among our leaders of our allied countries, he attacks businesses, he attacks all kinds of people except Putin and that tells me something."
Sen. Richard Blumenthal, a former prosecutor, says that President Donald Trump's tweet calling for Attorney General Jeff Sessions to end the Russia investigation comes close to the crime of obstruction of justice.
"There is now, right now, a clearly credible case of obstruction of justice against the President of the United States," Blumenthal said.
Other Senate Democrats called the tweet "regrettable."
Amid a series of morning tweets, Trump wrote , "This is a terrible situation and Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further. Bob Mueller is totally conflicted, and his 17 Angry Democrats that are doing his dirty work are a disgrace to USA!"
Mueller already is interested in some of Trump's tweets to the extent they raise obstruction of justice concerns.
In obstruction cases, prosecutors have to prove beyond a reasonable doubt that a particular act got in the way of an investigation and that the person who did it intended to obstruct.
White House officials said Trump's tweets are simply the president "fighting back." They dispute the notion that Trump was directing Sessions to take action.