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||The examples and perspective in this article may not represent a worldwide view of the subject. (December 2010)|
A provisional ballot is used to record a vote when there are questions about a given voter's eligibility. A provisional ballot would be cast when:
- The voter refuses to show a photo ID (in regions that require one)
- The voter's name does not appear on the electoral roll for the given precinct.
- The voter's registration contains inaccurate or out-dated information such as the wrong address or a misspelled name.
- The voter's ballot has already been recorded
Whether a provisional ballot is counted is contingent upon the verification of that voter's eligibility. Many voters do not realize that the provisional ballot is not counted until 7–10 days after election so their vote does not affect the calling of the states to different candidates.
A guarantee that a voter could cast a provisional ballot if he or she believes that they are entitled to vote was one of the guarantees of the Help America Vote Act of 2002.
The right of political parties to have observers at polling places is old. One of the established roles for such observers is to act as challengers, in the event that someone attempts to vote at the polling place who is not eligible to vote.
When a voter's right to vote was challenged, state laws typically allowed them to cast a challenged ballot. After the polls closed, the canvassing board was then charged with examining the challenged ballots and determining whether the challenge was to be upheld or not.
The right to a provisional ballot, as enacted by the Help America Vote Act, brings a degree of uniformity to the array of various challenged ballot rules enacted by various states.
Potential problems 
At their best, provisional ballots provide voters who would otherwise be turned away from the polls to have their votes counted, but at their worst, the offer of a provisional ballot can be "a way to brush off troublesome voters by letting them think they have voted." It is possible for parties to force certain voters to cast provisional ballots so they can suppress the vote total of an opponent being counted on election night.
In the 2004 US Presidential Election, controversy arose out of arguments regarding the interpretation of the criteria for determining the eligibility of voters using provisional ballots. Many allege that these discrepancies of interpretations, particularly in Ohio, may have been a deciding factor in the outcome of the election. In the 2004 election, at least 1.9 million provisional ballots were cast, and 676,000 were never counted due to various states' rules on counting provisional ballots.
Studies of the use of provisional ballots in the 2006 general election in the United States show that around 21% of provisional ballots were rejected, where the majority of rejected ballots were cast by registered voters and the majority of rejections were for reasons that were preventable.
Number of provisional ballots not counted in US elections 
According to the Election Assistance Commission thousands of provisional ballots are not counted each election.
2004 US Election
In the 2004 US Election 35.5 percent of all provisional ballots cast were discarded for various reasons. This meant a total of 675,676 votes were not counted. See 2004 EAC report here.
2006 US Election
In the 2006 US Election 20.5 percent of all provisional ballots cast were discarded for various reasons. This meant a total of 170,872 votes which were cast provisionally were not counted. See 2006 EAC report here.
Reasons for rejection 
The most common reason for rejection of provisional ballots is due to voters who have been purged off the voting rolls. 44 percent of those provisional ballots rejected in 2006 were due to this factor.
- Title XIV, Chapter 5, Sec. 4922, The Election Laws of the State of Ohio, Ohio Secretary of State, 1920.
- Election Day "Challengers", Minnesota Secretary of State, June 2008.
- Greg Brown, [www.earlcarl.org/publications/provisional%20ballots.pdf The Provisional Ballot vs. Challenged Ballot], Nov. 16, 2005.
- Douglas W. Jones, Reliability of US Voting Systems, Prepared Remarks for the Congressional Black Caucus Hearing on election preparedness October 7, 2004.
- Let The Recounts Begin (National Journal)
- Provisional Voting: Fail-Safe Voting or Trapdoor to Disenfranchisement, Advancement Project, Sept. 16, 2008