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==Nhược điểm==
===Đầu phiếu chiến thuật===
===Tactical voting===
Theo luật Duverger, hình thức đầu phiếu đa số tương đối khuyến khích kỹ thuật [[đầu phiếu chiến thuật]] ở mức độ lớn hơn các hình thức khác. Như là ''thỏa hiệp'', cử tri dường như bị ép bầu cho một trong hai ứng viên có cơ may thắng nhất, dù cho họ không thích ai trong số hai ứng viên đó bởi vì nếu họ bầu cho một ứng viên khác, họ sẽ lãng phí lá phiếu của họ.
To a much greater extent than many other electoral methods, plurality electoral systems encourage [[tactical voting]] techniques, like "compromising". Voters are pressured to vote for one of the two candidates they predict are most likely to win, even if their true preference is neither, because a vote for any other candidate will be likely to be wasted and have no impact on the final result. This is known as [[Duverger's Law]].
In the Tennessee example, if all the voters for Chattanooga and Knoxville had instead voted for Nashville, then Nashville would have won (with 58% of the vote); this would only have been the 3rd choice for those voters, but voting for their respective 1st choices (their own cities) actually results in their 4th choice (Memphis) being elected.
The difficulty is sometimes summed up, in an extreme form, as "All votes for anyone other than the second place are votes for the winner", because by voting for other candidates, they have denied those votes to the second place candidate who could have won had they received them. It is often claimed by [[United States]] [[Democratic Party (United States)|Democrats]] that Democrat [[Al Gore]] lost the [[U.S. presidential election, 2000|2000 Presidential Election]] to [[Republican Party (United States)|Republican]] [[George W. Bush]] because some voters on the left voted for [[Ralph Nader]] of the [[Green Party (United States)|Green Party]], who exit polls indicated would have preferred Gore to Bush 45 percent to 27 percent, with the rest not voting in Nader's absence.<ref>[http://query.nytimes.com/gst/fullpage.html?res=9B03E4D6173CF937A15751C0A9629C8B63 THE 2004 CAMPAIGN: THE INDEPENDENT; Relax, Nader Advises Alarmed Democrats, but the 2000 Math Counsels Otherwise - New York Times<!-- Bot generated title -->]</ref>
Such a mentality is reflected by elections in [[Puerto Rico]] and its three principal voter groups: the [[Puerto Rican Independence Party|Independentistas]] (pro-independence), the [[Popular Democratic Party of Puerto Rico|Populares]] (pro-[[Commonwealth (U.S. insular area)|commonwealth]]), and the [[New Progressive Party of Puerto Rico|Estadistas]] (pro-[[statehood]]). Historically, there has been a tendency for Independentista voters to elect Popular candidates and policies. This phenomenon is responsible for some Popular victories, even though the Estadistas have the most voters on the island. It is so widely recognised that the Puertoricans sometimes call the Independentistas who vote for the Populares "melons", because the fruit is green on the outside but red on the inside (in reference to the party colours).
Because voters have to predict in advance who the top two candidates will be, this can cause significant perturbation to the system:
A feature of the FPTP system is that invariably, voters can select only one candidate in a single-member district, whilst in multi-member districts they can never select more candidates than the number of seats in the district. Some argue{{Who|date=February 2009}} that FPTP would work better if electors could cast votes for as many candidates as they wish. This would allow voters to "vote against" a certain despised candidate if they choose, without being forced to guess who they should vote for to defeat that candidate, thus eliminating the need for tactical voting. Such a system would also serve to reduce the [[spoiler effect]]. This system is called [[approval voting]].
===Ảnh hưởng đến các đảng chính trị ===
===Effect on political parties===
[[Image:Percentage graph UK POLITICS 2005.png|right|thumb|400px|A graph showing the difference between the popular vote and the number of seats won by major political parties at the [[United Kingdom general election, 2005]]]]
[[Luật Duverger]] là một nguyên tắc trong [[khoa học chính trị]] cho rằng những hệ thống dùng đầu phiếu đa số tương đối trước sau gì cũng trở thành [[hệ thống lưỡng đảng]].
[[Duverger's law]] is a principle of [[political science]] which predicts that constituencies that use first-past-the-post systems will become [[two-party system]]s, given enough time.
First-past-the-post tends to reduce the number of political parties to a greater extent than most other methods, thus making it more likely that a single party will hold a majority of legislative seats. (In the [[United Kingdom]], 18 out of 22 General Elections since 1922 have produced a majority government.) Single party rule enables quicker decision-making with less back and forth negotiation.
Multi-party coalitions, on the other hand, require consent among all coalition partners to pass legislation, which gives small parties a disproportionate amount of power. In the UK, arguments for plurality often look to [[Politics of Italy|Italy]] where the frequent government changeovers are presented as undesirable. (This problem could be solved with [[separation of powers]], in which the entire government didn't have to turn over just because it lost a vote.)
FPTP's tendency toward fewer parties and more frequent one-party rule can also produce disadvantages. One such disadvantage is that the government may not consider as wide a range of perspectives and concerns. It is entirely possible that a voter will find that all major parties agree on a particular issue. In this case, the voter will not have any meaningful way of expressing a dissenting opinion through his or her vote.
As fewer choices are offered to the voters, voters may vote for a candidate with whom they largely disagree so as to oppose a candidate with whom they disagree even more (See tactical voting above). The downside of this is that candidates will less closely reflect the viewpoints of those who vote for them.
It may also be argued that one-party rule is more likely to lead to radical changes in government policy that are only favoured by a plurality or bare majority of the voters, whereas multi-party systems usually require greater consensus in order to make dramatic changes.
===Wasted votes===
{{Unreferenced section|date=June 2007}}
[[Wasted vote]]s are votes cast for losing candidates or votes cast for winning candidates in excess of the number required for victory. For example, in the [[UK General Election of 2005]], 52% of votes were cast for losing candidates and 18% were excess votes - a total of 70% wasted votes. This is perhaps the most fundamental criticism of FPTP, that a large majority of votes may play no part in determining the outcome. Alternative electoral systems attempt to ensure that almost all votes are effective in influencing the result and the number of wasted votes is consequently minimised.
===Manipulation charges===
The presence of [[spoiler (politician)|spoiler]]s often gives rise to suspicions that [[strategic nomination|manipulation of the slate]] has taken place. The spoiler may have received incentives to run. A spoiler may also drop out at the last moment, inducing charges that such an act was intended from the beginning.
===Disproportionate influence of smaller parties===
Smaller parties can disproportionately change the outcome of an FPTP election by swinging what is called the 50-50% balance of two party systems, by creating a [[political faction|faction]] within one or both ends of the [[political spectrum]] which shifts the winner of the election from an [[absolute majority]] outcome to a [[simple majority]] outcome favouring the previously less favoured party. In comparison, for electoral systems using [[proportional representation]] small groups win only their proportional share of representation. In the [[United States]], this mechanism falls within one major reasoning (USA, Voting act, 1970s) favoring two-party, First-past-the-post (FPTP) electoral systems.
===OtherLá aspectsphiếu lãng phí===
[[Lá phiếu lãng phí]] là những phiếu bầu cho những ứng viên thua hay cho những ứng viên thắng nhưng vượt quá ngưỡng cần thiết.
See [[single-winner voting systems]] for other disadvantages commonly associated with plurality, such as diminished representation, sweepout and other skewed results, and "safe seats".
===Việc ảnh hưởng bất tương xứng cảu các đảng nhỏ ===
Các đảng nhỏ có thể thay đổi một cách không tỉ lệ đến kết quả của cuộc bầu cử theo dạng này bằng cách tạo ra bè phái chính trị. Nhất là khi có hai đảng đang cân bằng nhau, nếu các đảng nhỏ này tham gia vào một bên sẽ tạo lợi thế cho đảng trước đó ít được ưa chuộng hơn. So sánh với [[đại diện tỷ lệ]], các đảng nhỏ này chỉ đơn giản là giành được tỉ lệ phần trăm họ thắng mà thôi.
===Issues specific to particular countries===
====Solomon Islands====
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