"I agree that he that he's committed high crimes and misdemeanors. I agree that he's a clear and present threat to the national security of the United States," Lockhart told ABC News Chief White House Correspondent Jonathan Karl and Political Director Rick Klein on the Powerhouse Politics podcast Wednesday.
"I believe, based on my own experience, particularly during the Clinton administration, that if the Democrats move to impeach him knowing full well that he will never be convicted in the Senate … that actually might help Trump," Lockhart said.
Lockhart has a long and varied resumé, including work as press secretary for several presidential campaigns, and his tenure as White House press secretary under President Bill Clinton between 1998 and 2000.
Lockhart said his biggest fear is that impeachment goes to the Senate and fails, sending a message to undecided American voters that Trump was acquitted by the Senate.
He also fears the attention impeachment proceedings would draw attention away from issues that Democrats will run on, like health care, climate change and tax policy.
"If you have a big, shiny object like impeachment hearings, nothing else will break through," Lockhart said.
As Clinton’s impeachment neared, Lockhart pointed out, his approval ratings increased.
"When he was impeached his job approval was 73 percent. I mean if they could have impeached him twice he would have gotten into the 80s," Lockhart said.
Lockhart said that Democrats have a lot of other options available besides impeachment.
"We could do hearings through all through the summer and then censure him on the floor," Lockhart said. "If we're looking to stain his presidency, that would stain his presidency."
Karl also asked Lockhart about findings in the Mueller report that current White House press secretary Sarah Huckabee Sanders made contradictory statements to the press.
Lockhart said that he saw role of press secretary as twofold. The first requirement, he said, is to be available to White House reporters, which includes holding briefings on a regular basis.
"And then simply tell the truth," Lockhart said. "When threatened with going to jail she told the truth. When not being threatened with going to jail she makes stuff up."
Klein asked Lockhart to weigh in on former vice president Joe Biden’s presidential bid, which Biden is set to announce Thursday morning.
Lockhart, who said he’s known Biden for 40 years, said he thinks Biden’s candidacy has the potential to shape the strategy of the 2020 race.
If, over the next two or three months, Biden can prove himself as a strong frontrunner, "that will dictate the rest of the race," Lockhart said.
"Then it will be a fight between 19, 20 people to figure out who's the alternative," Lockhart said.
He added that presidential politics are especially unpredictable, and it is possible Biden’s campaign may not gain the momentum it hopes for.
"Then the race remains completely unstructured," Lockhart said, and the election may go well into the primaries and caucuses before it sorts itself out.
Powerhouse Politics podcast is a weekly program that posts every Wednesday, and includes headliner interviews and in-depth looks at the people and events shaping U.S. politics. Powerhouse Politics podcast is hosted by ABC News Chief White House Correspondent Jonathan Karl and ABC News Political Director Rick Klein.