Biden’s Fate Hangs Over Baldwin and Democrats in Congress as Voters Question His Fitness

Senator Tammy Baldwin, a Wisconsin Democrat seeking re-election, has noticed voters returning to the same question in recent days as she crisscrosses her state to make the case for her campaign: Does she think President Biden can win in November, and should he even try?

“Typically, I’ll go to an event; I’ll share my remarks,” Ms. Baldwin said in an interview on Friday at a newly opened campaign office in southwestern Wisconsin. “And then people come up one by one and — at first in a whisper — are really concerned.”

A soft-spoken two-term senator who has carved out a reputation for her cross-party appeal, Ms. Baldwin easily cruised to victory in 2018, and her race this year was never expected to be ultracompetitive, even in this crucial swing state. But rising concerns about Mr. Biden’s age and fitness to run have introduced new risks for Democratic candidates like Ms. Baldwin just 100 days out from Election Day, imperiling even seats that were once considered relatively safe for the party.

That has left Democrats already anxious about losing the White House to former President Donald J. Trump contemplating the prospect of widespread losses in Congress that could leave the party locked out of power altogether during a Trump presidency and well beyond.

In recent days, as Democratic leaders have privately pressed Mr. Biden to step aside, two other senators up for re-election, both in the tightest races in the nation — Senators Jon Tester of Montana and Sherrod Brown of Ohio — have called on Mr. Biden to step aside. It comes as Democrats have received polling suggesting that voters distrust elected officials who vouch for Mr. Biden’s mental capacity and endorse his candidacy.

In an interview, Ms. Baldwin declined to do either vouch for Mr. Biden or to call on him to step aside, saying only that she was conveying “as strongly as possible to the White House” the mounting concerns she has been hearing.