"dark horse"
a person who is running for office is a candidate
A candidate.
Presidential Candidate
The vice presidential candidate is often referred to as the running mate of the presidential candidate during the campaign.
Unknown candidates do not have any particular name. People will announce are running. Some are nominated by obscure parties and are put on the ballot in some states. Third parties candidates sometime attract a significant number of votes, but they are hardly unknown. A darkhorse is a candidate who was not expected to win the nomination, but is nominated by a major party.That may the term you are thinking of.
A candidate.
A person running for political office is called a candidate. Candidates typically represent a political party or run as independents, and they seek election to a specific position such as president, senator, mayor, or council member. During their campaign, candidates present their platform and policies to voters in the hopes of winning their support and ultimately being elected to the office they are seeking.
An unknown nominated candidate is often referred to as a dark horse candidate. This term is used to describe a candidate who is not well-known or expected to win, but unexpectedly gains popularity or success in an election or nomination process.
The two men who ran for Vice President were Joseph Biden (Democrat) and Paul Ryan (Republican). Since President Obama won re-election in 2012, and Joe Biden was his running-mate, Mr. Biden won a second term as Vice President.
The word "secede" seems strange here. People say a candidate withdrew or dropped out of the race, if he stopped seeking the nomination.
The fear of the unknown is called xenophobia.
The part of the constitution that establishes the presidency is called Article II.