By Bridget Nolan and Dana Bash, CNN

(CNN) -- Former Democratic Senate Leader Harry Reid has some advice for the Democrats running for president in 2020: It's not all about Donald Trump.

"[They] need not talk about how bad President Trump is, they just need to talk about what's good for the country," he said.

Reid said even voters supporting the President know what problems he has, and he hopes people understand that the Trump presidency has been bad for the country.

During an exclusive interview in Reid's office at the Bellagio hotel in Las Vegas, we went through some of the 2020 hopefuls. If former Vice President Joe Biden decides to run, Reid says other candidates will have to catch up with him. He says former Rep. Beto O'Rourke hasn't been tested yet. And he says Sen. Kamala Harris is somebody to be "looked at closely."

A potential candidate he is not to fond of: former Starbucks CEO Howard Schultz, whose potential independent bid Reid said could end up being an asterisk in history.

Reid takes great pride in being one of the first of Barack Obama's Senate colleagues to encourage him to run for president.

"I called him into my office and told him he should take a look at it. He was stunned because I was first to suggest it to him," Reid told us a few years ago.

With that history of picking a winner, it's no surprise that several would-be and declared 2020 presidential contenders have checked in with Reid.

"I've had the good fortune of having a number of them come and see me at my home, the people that are considering running," he said.

"I think it's wonderful that we have this wide range of talented people," he said.

Former Vice President Joe Biden

"Joe Biden's been to my home, spent an hour and a half with me. I think so much of him ... His life story is something that is tearful. We were flying from Indianapolis to Reno, Nevada. I'll never forget that story of Joe Biden telling me about his wonderful love that he met on a beach in Florida some place. And the tragic accident where his daughter was killed, his wife was killed. His two boys, he and his sister raised them. I just admire him so very, very much, and his government service has been very, very significant. And still feel for him, his loss of Beau. That was tragic."

Reid said running for president is a "personal decision" for Biden, and if he did choose to run he thought the other candidates would "have to catch up with him."

Reid thought if Biden did get into the race he would have a chance at winning.

"I think any Democratic candidate that's on that list of 23 or whatever it is can win, and certainly Joe Biden's on that list," he said.

Sen. Elizabeth Warren

"I needed somebody for my debt commission, and I'd read about her, looked at one of her books and I invited her down to my office, she and her daughter. Harvard professor, very academic looking woman. She's just been remarkable, everything that she's touched ... I certainly would not, have not, nor would not ever discourage her from running for president."

Reid respects the fact that Warren is engaging so actively with the President.

Sen. Cory Booker

"Cory's mom lives here [in Nevada]. Cory's dad died here. So I know Cory Booker very very well. I admire him, a Rhodes scholar. Tight end at Stanford. You know, he's quite a guy. So, and I talked to him I guess day before yesterday ... We haven't sat down face to face for a while. We'll do that again. He's coming out soon to visit his mom, and he'll set some time aside for me."

When asked whether Booker would be a good president, Reid replied, "I can't think of any one of the Democrats that have put their name up for consideration that would be a bad president."

Sen. Amy Klobuchar

Reid has been impressed with Klobuchar over their years of serving together in the Senate, he even suggested she be nominated for the Supreme Court if Hillary Clinton had won the election in 2016.

"Her background is stunning. Yale, law review. Her background is a prosecutor out of the state of Minnesota. She was Senator. I thought she was perfect to go on the Supreme Court."

When asked whether there was any truth to the story that Reid had to pull Klobuchar aside and say, "Go easy on your staff," he replied, "I don't know where stuff like that comes from. If I did that, I have honestly no memory of it. It doesn't sound anything like I would do."

Sen. Kamala Harris

"We've talked. I met her, I've met her. We've talked on the telephone, and I think she's somebody to be looked at very closely. Why? For a number of reasons. Number one, she has a great story. Number two, she comes from California. And that state has a very early primary now. They moved it up significantly, and she comes out of that state. She could come out of California almost 30% of the delegates. You have 49 states to pick up another 21%."

Mike Bloomberg

"I think Mike Bloomberg, who I've talked to, I think he has an outstanding chance to really reshape America. Here's a man who has the resources to help parties. One of the strengths I developed over the years into that was I focused on grassroots in Nevada and build up a tremendously strong political organization in Nevada. He has the resources to do that all over the country. I think he has a lot of potential."

Former Rep. Beto O'Rourke

"I don't know the man. I don't know Beto O'Rourke. I think when you're a new candidate like Beto O'Rourke, you have to be tested because you, the press, love to have virgins out there, and they go after them pretty quickly. So he's not tested yet."

Howard Schultz

"I've met Howard Schultz -- don't like his independent streak. I think that he'll wind up being another asterisk in an article in some history book. I think that we've tried that in recent years and it just hasn't worked very well."

Sen. Sherrod Brown

"I worked hard to get him to run for the Senate. I'm glad that he did. He has a stunningly impressive wife. I think she won a Pulitzer Prize. I think he would be a good president, and I think he would sell. He's kind of the working class kind of guy."

Sen. Michael Bennet

"Michael Bennet is one of my favorite senators ... He's such a nice man. I wish I could give you other traits of Michael Bennet, but he has traits like the first President Bush, his strength was just was nice to everybody, and I think that's Michael's greatest asset."

Sen. Kirsten Gillibrand

"Kirsten Gillibrand is a tremendously competent person. Kirsten Gillibrand, look at her political work up. She started on heavily Republican district, she won that, she's now very, very strong in New York which is not a very conservative place. And I think that she's spending a lot of time talking about the importance of feminism in politics. I don't think that's a waste of time. I think it's good she's doing that."

Sen. Bernie Sanders

Reid spoke about Bernie Sanders in the context of the new invigorated liberal wing of the party. When asked whether it makes him nervous or excited he replied, "I think that my perspective as you look at the Democratic caucus that leader (Nancy) Pelosi has, everyone thinks it's gonna be a left leaning, oh so much different from the past. But remember her strength has come from Democrats picking up Republican seats. So I think Pelosi, she hasn't told me this, it's just my opinion, I think her caucus is gonna be a fairly centrist caucus. I think that these people who are out with all these ideas, that's wonderful, that's good. Because I know that Bernie Sanders, I think they're ideas that were really on the fringe that he sort of started talking about, people are now accepting them as brave, good ideas. Doing something to make sure it's easier for young men and women to go to college. Make sure that we do something to take care of health care."

On managing so many 2020 senators

The fact that so many members of the Democratic Senate caucus are either already running for president or may be soon could pose a challenge for Reid's successor, Democratic leader Chuck Schumer.

But Reid says, no.

"I think that would be really easy," he admitted.

"They're afraid to miss many votes so they rarely do that. So I don't think it's a big problem at all," he added.

He remembers when he was leader and had to deal with members of his caucus running for president. But not this many people, he admits.

"This is a lot," he said with a smile.