KABUL, Afghanistan — Three months after Afghanistan’s presidential vote, the entire electoral process is stalled in a dispute that Afghan and Western officials say could pose an even greater threat to stability than the last such crisis, five years ago.

Supporters of opposition candidates have besieged half a dozen election offices around the country for weeks, vowing to fight rather than accept another United States-brokered compromise like the one that resolved the 2014 dispute. Security officials worry that one wrong move could tip the protests into bloodshed. And election officials say a biometric verification process that was supposed to prevent voter fraud may have been compromised by human error.

In the middle of it all — again — is Abdullah Abdullah, making his third attempt to become president, and for the third time falling into a bitter standoff with election officials.

This one is likely to play out differently. With American diplomacy focused on negotiating an end to the long war with the Taliban, Western officials say the United States has made it clear that it will not be stepping in as it did five years ago. Then, Secretary of State John Kerry negotiated a power-sharing deal between Mr. Abdullah, now Afghanistan’s chief executive, and Ashraf Ghani, now the president, that Mr. Kerry said averted a civil war.