Mr Bossie tested positive on Monday.
Maggie Haberman of the New York Times reported that Mr Lewandowski was at the White House election night party, as was Mr Bossie.
Mr Lewandowski is now the sixth person at that White House party to have contracted Covid-19, after Mr Bossie; Housing and Urban Development Secretary Ben Carson; White House chief of staff Mark Meadows; Brian Jack, the White House political affairs director, and Healy Baumgardner, a former White House aide who now works in private equity.
He believes he caught it in Philadelphia, she said. It was unclear how he knew.
Mr Lewandowski was Mr Trump’s first campaign manager; a role he undertook from January 2015 to June 2016, when he was replaced by Paul Manafort. Mr Manafort was in turn replaced by Steve Bannon and Kellyanne Conway.
There has been no official confirmation of Mr Lewandowski’s diagnosis.
He was in Philadelphia alongside Mr Giuliani on Saturday, at the infamous Four Seasons Total Landscaping press conference where they found out live on air that Joe Biden had been declared the projected winner of the election.
The 3 November White House event is now being seen, to the surprise of few, as a “super-spreader event”.
The gathering was held in the East Room, and there was little evidence of mask-wearing or social distancing, despite a spate of recent infections among top administration officials.
It is the second time the White House has been hit by a spate of cases.
At the end of September and into early October there were at least 36 confirmed cases, following a large gathering in the Rose Garden on 26 September to celebrate Amy Coney Barrett’s nomination to the Supreme Court.
Mr Trump was confirmed positive on 1 October and the following day was taken to the Walter Reed National Military Medical Centre for three days.
He emerged triumphant and defiant, urging Americans not to let Covid concerns “dominate your life”.
There have now been 237,000 deaths and over 10 million cases,
Another smaller outbreak occurred among Vice President Mike Pence’s staff two weeks ago. Several aides to the vice president, including his chief of staff, tested positive ahead of the 2020 election, forcing some aides off the campaign trail.
Despite all the outbreaks within the White House alone, Mr Trump has not enforced stricter mask wearing or social distancing guidelines on the grounds.
He and his administration staff continued to hold large gatherings and rallies after the first outbreak, and Mr Pence stayed on the campaign trail despite being in close contact with coronavirus-positive staff members.
These decisions have called into question the Trump administration’s response to the pandemic at a time when cases are surging across the United States.
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