"I'm running for president of the United States and I'm very excited about it," she said with a grin. "I love my country. This is a moment in time that I feel a sense of responsibility to stand up and fight for the best of who we are, and that fight will always include as one of the highest priorities, our national security, and thinking about it in a way that we understand that we must be smart."
She subtly shaded President Donald Trump, without mentioning him by name, for pushing away American allies and damaging the United States' "moral authority" in the world.
"We must understand that power that we have," she said in her first televised pitch to voters. "The strength that we have that is about military power, it is about diplomatic power, it is about the power that we have in terms of what has been -- until recently -- our moral authority in the world and our ability to work with our allies."
Later in the conversation with "GMA" anchors George Stephanopoulos and Robin Roberts, the former California prosecutor, who was elected to the Senate in 2016, said President Trump has "absolutely" compromised the American peoples' faith in the "integrity of our system of justice."
When asked to respond to concerns she doesn't have enough experience working in government at the federal level, she touted her "leadership skills, experience and integrity," and promised to "fight" for the American people.
"On all of those points, I feel very confident about my ability to lead," she said. "I feel very confident about my ability to listen and to work on behalf of the American public. The American public wants a fighter, and they want someone that is going to fight like heck for them and not fight based on self-interests. I'm prepared to do that."
Senator Harris said it was "very important" to announce her candidacy in an already crowded Democratic primary field on MLK Day.
"The thing about Dr. King that always inspires me is that he was aspirational. He was aspirational like our country is aspirational. We know that we've not yet reached those ideals. But our strength is that we fight to reach those ideals, and that inspires me. Because it is true we are a country that -- yes, we are flawed, we're not perfect, but we are a great country when we think about the principles on which we were founded. So today, the day we celebrate Dr. King, is a very special day for all of us as Americans and I'm honored to be able to make my announcement on the day we commemorate him."
Since Harris sits on the Senate Intelligence Committee, Stephanopoulos also asked if she has seen any evidence from special prosecutor Bob Mueller's investigation that would warrant impeaching Trump.
"I can not talk about the evidence I have received...but I will say there is no question that Bob Mueller is conducting an investigation with the highest level of integrity. He is clearly taking the job very seriously, there have already been 33 indictments, and it is incumbent on the United states congress to do everything in our power to make sure that his investigation is whole and will be complete without any interference."
Other Democrats who have officially thrown their hat in the Democratic primary ring include former Secretary of Housing and Urban Development Julián Castro of Texas, Representative Tulsi Gabbard of Hawaii, former Representative John Delaney of Maryland, former congressional candidate Richard Ojeda of West Virginia and businessman Andrew Yang of New York.