In the upcoming debate between Joe Biden and Donald Trump, both candidates will have to grapple with significant political vulnerabilities that could either be assuaged or amplified on the debate stage. Recent CBS News/YouGov polls shed light on these weaknesses, highlighting the challenges that lie ahead for each contender.

Biden, at 81 years old, faces concerns regarding his age and mental acuity. Though only three years older than Trump, voters are more than 10 times as likely to cite his age as a factor of consideration. Given these reservations, it is likely that voters have limited expectations for Biden's performance on Thursday. A coherent, agile, and forceful presentation that spans 90 minutes could potentially alter how Americans perceive him. Conversely, a muddled and faltering display could reinforce existing doubts and create new ones.

On the other hand, Trump carries the weight of nearly a decade filled with controversies and inflammatory actions. This is evident when voters assess each candidate's behavior. In an early June CBS News/YouGov poll, 67% of voters expressed personal dislike for how Trump has conducted himself, compared to 51% for Biden. Among independents, these figures rose to 74% for Trump and 55% for Biden.

The reason Biden remains neck-and-neck with Trump in polling is partly due to a significant portion of the current president's support driven by opposition to the former president. In a mid-June CBS News/YouGov poll, 33% of Biden supporters stated they liked the president, while 48% said their motivation was to oppose Trump. Among independent Biden backers, 21% liked the president, while 67% opposed Trump.

For Trump, the worst-case scenario is that this antipathy imposes a ceiling on his support, with too many voters feeling too unnerved to back him, regardless of their view on Biden. It is unlikely that any kind of performance on Thursday would significantly alter Trump's image. However, in an election where margins matter, even swaying a small fraction of apathetic Biden supporters could be all Trump needs. Conversely, if Trump merely confirms the reservations that voters have about him, it may be enough to secure Biden's advantage.

In Erie, Pennsylvania, a critical county in a crucial swing state, Nikki Haley's former supporters are still searching for a political home. Many of these voters, such as Richard Speicher and Mary Gensheimer, voted for Haley in the GOP primary, even though she had already exited the race. Speicher explained that Trump does not represent the Republican Party as they know it, and Haley was their preferred choice. Their story reflects a broader segment of swing voters who remain undecided and may ultimately choose between supporting President Biden or casting another protest vote in the upcoming general election.

Erie County, with its bellwether status, voted for the winner of both the state and the presidency in the past four elections. Haley's ability to secure almost 20% of the primary vote in Erie County, even after she had withdrawn, is concerning for Trump's re-election prospects. Statewide, she received 16.4% of the vote, approximately 159,000 votes, in Pennsylvania—a state Trump won by 44,000 votes in 2016 and Biden won by 80,000 votes in 2020.

While Haley has announced her intention to vote for Trump in November, not all of her supporters are ready to follow suit. The Biden campaign has recognized this opening and has intensified efforts to appeal to Haley voters, employing advertisements, expanding staff, and relying on volunteers.

Richard Speicher plans to replace the missing "Republican voters against Trump" sign with a Biden sign, feeling disillusioned with the direction of the Republican Party. As he contemplates his political future, Speicher echoes the sentiment of many others, stating that the Republican Party he once knew is now deceased, leaving him uncertain about his next move.

As the debate approaches, both Biden and Trump are aware of the weaknesses they must address. While Biden aims to counter doubts about his mental sharpness, Trump hopes to navigate around a history of controversies. Their performances on Thursday will play a crucial role in potentially swaying swing voters who remain undecided in this fiercely contested election.