The 25th Amendment is not voted on by the electorate but only initially through the cabinet and then followed on by Congress. The same with impeachment. While yes Biden is declining and worrying so so far he has been able to negotiate with foreign leaders including getting Europe to continue to act on Ukraine recently and with Asian leaders on mutual defense. My own view is that Biden will eventually withdraw from the race but I don't think he is far from incapable. You're entitled to your own opinion but US alliances are far stronger than they have been in years and for all of the turmoil that the World is facing Biden has still kept mass deployment of US troops out of harms way. In fact there are less US troops now in active war zones than there were doing Trump.
Section 4 of the 25th Amendment is not just for emergencies. If the President is unwilling or unable to acknowledge their incapacity to perform duties, my understanding is that this could include a medical emergency, significant cognitive decline or psychological dysfunction, and extreme behaviors that pose a national security risk or threaten the well-being of the nation. Spoiler **Section 4.** Whenever the Vice President and a majority of either the principal officers of the executive departments or of such other body as Congress may by law provide, transmit to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office, the Vice President shall immediately assume the powers and duties of the office as Acting President. Thereafter, when the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that no inability exists, he shall resume the powers and duties of his office unless the Vice President and a majority of either the principal officers of the executive department or of such other body as Congress may by law provide, transmit within four days to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office. Thereupon Congress shall decide the issue, assembling within forty-eight hours for that purpose if not in session. If the Congress, within twenty-one days after receipt of the latter written declaration, or, if Congress is not in session, within twenty-one days after Congress is required to assemble, determines by two-thirds vote of both Houses that the President is unable to discharge the powers and duties of his office, the Vice President shall continue to discharge the same as Acting President; otherwise, the President shall resume the powers and duties of his office.
