When the bankers and lawyers for Capital One and Discover were locked in tense negotiations in February over the timing for the merger of their companies, political factors loomed.

Move too quickly, three people involved in those discussions recalled, and the Biden administration could try to scuttle a tie-up that would make executives on both sides rich. Wait longer, and former President Donald J. Trump might return to office and be more amenable. The companies agreed to aim for a Dec. 31 deal completion — a date between the election and the inauguration.

Eight months later, advisers to the bank and credit card company have decided that the best time to get the deal done might be the present, said the three people, who asked for anonymity because of regulatory rules about speaking publicly. They are racing to hit the year-end deadline in part because of the fear that Mr. Trump, who recently proposed a cap on credit-card interest rates and unveiled a new cryptocurrency company to challenge what he called “slow and outdated big banks,” would look unkindly toward helping two big lenders merge.

This year’s presidential election is vexing Wall Street, where fortunes can rise and fall on the whims of Washington. With neither candidate an obvious friend to financiers, and both pledging crackdowns on bankers in their own respects, the heartbeat of the financial services industry is pulsing with anxiety.

That is, to the degree that it’s pumping at all. Since President Biden dropped out of the race, the uncertainty has only increased and newly announced acquisitions and public stock offerings — proxies for corporate optimism — have been hushed.

In interviews, bankers, lawyers and advisers who support both candidates, as well as those still undecided, listed a number of outstanding political questions that could create or wipe out fortunes. Would corporate taxes rise or fall? Would Vice President Kamala Harris’s proposals to tackle inflation crack down on profits? Which version of Mr. Trump would show up in office?