of votes, then that party will win 15% of the seats in the legislature. This is termed proportional representation or more accurately as party-proportional representation. Political scientists speculate that proportional representation leads logically to multi-party systems, since it allows new parties to build a niche in the legislature: In contrast, a voting system that allows only a single winner for each possible legislative seat is sometimes termed a plurality voting system or single-winner voting system and is usually described under the heading of a winner-takes-all arrangement. Each voter can cast a single vote for any candidate within any given legislative district, but the candidate with the most votes wins the seat, although variants, such as requiring a majority, are sometimes used. What happens is that in a general election, a party that consistently comes in third in every district is unlikely to win any legislative seats even if there is a significant proportion of the electorate favoring its positions. This arrangement strongly favors large and well–organized political parties that are able to appeal to voters in many districts and hence win many seats, and discourages smaller or regional parties. Politically oriented people consider their only realistic way to capture political power is to run under the auspices of the two dominant parties. In the U.S., forty-eight states have a standard winner-takes-all electoral system for amassing presidential votes in the Electoral College system. The winner-takes-all principle applies in presidential elections, since if a presidential candidate gets the most votes in any particular state, all of the electoral votes from that state are awarded. In all but two states, Maine and Nebraska, the presidential candidate winning a plurality of votes wins all of the electoral votes, a practice called the unit rule. Duverger concluded that "plurality election single-ballot procedures are likely to produce two-party systems, whereas proportional representation and runoff designs encourage multipartyism." He suggested there were two reasons why winner-takes-all systems leads to a two-party system. First, the weaker parties are pressured to form an alliance, sometimes called a fusion, to try to become big enough to challenge a large dominant party and, in so doing, gain political clout in the legislature. Second, voters learn, over time, not to vote for candidates outside of one of the two large parties since their votes for third party candidates are usually ineffectual. As a result, weaker parties are eliminated by voters over time.