Even Biden's campaign is wondering how Kamala Harris would perform against Trump

• The Biden campaign conducted a survey measuring Kamala Harris' performance against Donald Trump.
• In an internal memo, the campaign insisted that no other nominee would perform better than Biden.
• The survey comes ahead of a make-or-break presser, where Biden will speak unscripted.

Despite President Joe Biden's insistence that he is staying in the race, his campaign is testing Kamala Harris' strength against Donald Trump. The campaign's analytics team conducted a survey this week that measures her performance in a head-to-head battle against the former president, the New York Times reported.

It is seemingly the first time that the Biden camp is measuring Harris' chances after the debate, though other pollsters have been acutely interested in her since the disastrous night. Three sources informed about the survey declined to tell The Times why the campaign conducted it and how they plan to use the results.

The revelation comes ahead of a key press conference this evening, where Biden will host his first solo news conference in eight months. All eyes will be on the president during the unscripted event, which many consider a litmus test for his campaign.

The Biden campaign on Thursday circulated an internal memo arguing that there is a "clear pathway ahead" and claiming there are no signs that another candidate would outperform Biden against Trump.

"Hypothetical polling of alternative nominees will always be unreliable, and surveys do not take into account the negative media environment that any Democratic nominee will encounter," the memo read.