The compact is designed to ensure that the candidate who receives the most votes nationwide is elected president, and it would come into effect only when it would guarantee that outcome.

Taking the form of an interstate compact, the agreement would go into effect among participating states only after they collectively represent an absolute majority of votes (currently at least 270) in the Electoral College.

In addition to the adoption threshold, the NPVIC raises potential legal issues, discussed in § Constitutionality, that may draw challenges to the compact.

The project has been supported by editorials in newspapers, including The New York Times,[9] the Chicago Sun-Times, the Los Angeles Times,[21] The Boston Globe,[22] and the Minneapolis Star Tribune,[23] arguing that the existing system discourages voter turnout and leaves emphasis on only a few states and a few issues, while a popular election would equalize voting power.

Journalist and commentator Peter Beinart has cited the election of Donald Trump, whom some, he notes, view as unfit, as evidence that the Electoral College does not perform a protective function.

The adjacent maps illustrate the amount spent on advertising and the number of visits to each state, relative to population, by the two major-party candidates in the last stretch of the 2004 presidential campaign.

[35] Critics of the compact argue that candidates would have less incentive to focus on regions with smaller populations or fewer urban areas, and would thus be less motivated to address rural issues.

[38] Pete du Pont argues that the NPVIC would enable electoral fraud, stating, "Mr. Gore's 540,000-vote margin [in the 2000 election] amounted to 3.1 votes in each of the country's 175,000 precincts.

[36] Some supporters and opponents of the NPVIC believe it gives one party an advantage relative to the current Electoral College system.

Former Delaware Governor Pete du Pont, a Republican, has argued that the compact would be an "urban power grab" and benefit Democrats.

[40] New Yorker essayist Hendrik Hertzberg concluded that the NPVIC would benefit neither party, noting that historically both Republicans and Democrats have been successful in winning the popular vote in presidential elections.

"[39] In all four elections since 1876 in which the winner lost the popular vote, the Republican became president; however, Silver's analysis shows that such splits are about equally likely to favor either major party.

[44][45][46] Some opponents of a national popular vote contend that the non-proportionality of the Electoral College is a fundamental component of the federal system established by the Constitutional Convention.

Individual votes combine to directly determine the outcome, while the intermediary measure of state-level majorities is rendered obsolete.

[52] Duverger's law holds that plurality elections do not generally create a proliferation of minor candidacies with significant vote shares.

[62][63] With respect to vertical balance of power, the NPVIC removes the possibility of contingent elections for President conducted by the U.S. House of Representatives.

The Supreme Court has also held that congressional consent is required for interstate compacts that alter the horizontal balance of power among the states.

[71][72] The CRS report concluded that the NPVIC would likely become the source of considerable litigation, and it is likely that the Supreme Court will be involved in any resolution of the constitutional issues surrounding it.

[75] Proponents of the compact have argued that states have the plenary power to appoint electors in accordance with the national popular vote under the Elections Clause of Article II, Section I.

[84][85][86][87] Due to a lack of a precedent and case law, the CRS report concludes that whether states are allowed to appoint their electors in accordance with the national popular vote is an open question.

[89] A 2007 Washington Post and Kaiser Family Foundation poll found that 72% favored replacing the Electoral College with a direct election, including 78% of Democrats, 60% of Republicans, and 73% of independent voters.

[90] A November 2016 Gallup poll following the 2016 U.S. presidential election showed that Americans' support for amending the U.S. Constitution to replace the Electoral College with a national popular vote fell to 49%, with 47% opposed.

[103] Since the 1940s, when modern scientific polling on the subject began, a majority of Americans have preferred changing the electoral college system.

[108] In 2001, "two provocative articles" were published by law professors suggesting paths to a national popular vote through state legislative action rather than constitutional amendment.

[111] A few months later, Yale Law School professor Akhil Amar and his brother, University of California Hastings School of Law professor Vikram Amar, wrote a paper suggesting states could coordinate their efforts by passing uniform legislation under the Presidential Electors Clause and Compact Clause of the Constitution.

[111] To promote NPVIC, Koza, Fadem, and a group of former Democratic and Republican Senators and Representatives, formed a California 501(c)(4) non-profit, National Popular Vote Inc. (NPV, Inc.).

In Maine, an initiative to join the National Popular Vote Interstate Compact began collecting signatures on April 17, 2016.

On February 17, 2021, the North Dakota Senate passed SB 2271,[150] "to amend and reenact sections ... relating to procedures for canvassing and counting votes for presidential electors".

[151] The bill is an indirect effort to stymie the efficacy of the NPVIC by prohibiting disclosure of the state's popular vote until after the Electoral College meets.

[152][153] Later the bill was entirely rewritten as only a statement of intent and ordering a study for future recommendations, and this version was signed into law.