Former President Donald Trump has expanded his lead over President Joe Biden in the wake of the CNN presidential debate in which his opponent's performance reignited concerns over his age and fitness for office.

During the debate, Biden stumbled over his answers and often appeared lost on stage. The affair was widely regarded as a Trump victory and the Biden campaign has since rebuffed calls for him to drop out in favor of another Democratic candidate.

Heading into the debate, Trump led Biden by 3% among likely voters in the New York Times/Siena College poll and by 6% among registered voters. In that survey's first post-debate data, however, Trump led Biden by 6% among likely voters and by 9% among registered voters.

Among likely voters, Trump led Biden 49% to 43%. Among registered voters, the margin was 49% to 41% in favor of the 45th president. The outlet rounded the results.

Notably, Biden's support for remaining the Democratic nominee fell among the party rank and file. Prior to the debate, 52% of Democrats supported keeping him as the party's standard bearer, compared with 48% who held that position after the debate.

By contrast, Trump made modest gains within the GOP, with 80% of Republicans saying he should remain the nominee before the debate and 83% saying so after.

Seventy-four percent of voters indicated that Biden was too old for the job while only 42% said the same of Trump.

Conducted June 28-July 2, the survey questioned 1,532 voters.