But Sir Keir and Mr Sunak registered similar scores when compared across a range of leadership skills, according to the latest Ipsos UK Political Pulse survey taken at the start of February.
Sir Keir was rated higher than Mr Johnson on eight out of 10 leadership qualities, with the biggest gaps in favour of the Labour leader on attention to detail (27 percentage points), honesty (26) and being in touch with ordinary people (16).
Mr Johnson only scored higher than Sir Keir when respondents were asked who had “more personality” (24 percentage points) and was good in a crisis (four).
Mr Sunak was rated better than the Prime Minister in nine of the 10 attributes, with attention to detail showing the biggest gap in favour of the Chancellor (32 percentage points).
The results comparing Sir Keir and Mr Sunak showed the Labour leader slightly ahead in seven categories, with the biggest gap on the question of being in touch with ordinary people (12 percentage points).
Sir Keir was also slightly ahead of the Chancellor on understanding the problems facing the UK, being a capable leader and honesty.
Mr Sunak scored higher than Sir Keir on being good in a crisis (12 percentage points) and was marginally ahead on attention to detail.
The survey, which questioned a representative sample of 1,143 voters, also found 33% of voters think a Labour Government led by Sir Keir would do a better job of running the country than the Conservatives under Boris Johnson, an increase of 7% since the poll conducted in June.
Of the Conservative voters who took part, 44% said Mr Sunak replacing Mr Johnson as leader would make no difference to how the country was run.
But 34% said the Chancellor would do a better job than the Prime Minister, with 9% saying Mr Sunak would do worse in the role.
Labour also received its highest favourability score since the Ipsos poll was first conducted just before the General Election in 2019 (37%), with the Conservatives score one percentage point down from the January findings (25%).