This is an illegal compact among several states unless Congress approves. The people pushing this idea say it will kick in when enough states for a majority of electors agree to the compact. But they can not do that without Congress approving.
It's certainly Constitutional for the states to award their electors however they like. But it is not for the states to enter into an illegal compact.
Doesn't look like it.
Congressional consent is not required for the National Popular Vote compact under prevailing U.S. Supreme Court rulings. However, because there would undoubtedly be time-consuming litigation about this aspect of the compact, National Popular Vote is working to introduce a bill in Congress for congressional consent.
The U.S. Constitution provides:
“No state shall, without the consent of Congress,… enter into any agreement or compact with another state….”
Although this language may seem straight forward, the U.S. Supreme Court has ruled, in 1893 and again in 1978, that the Compacts Clause can “not be read literally.” In deciding the 1978 case of U.S. Steel Corporation v. Multistate Tax Commission, the Court wrote:
“Read literally, the Compact Clause would require the States to obtain congressional approval before entering into any agreement among themselves, irrespective of form, subject, duration, or interest to the United States.
“The difficulties with such an interpretation were identified by Mr. Justice Field in his opinion for the Court in [the 1893 case] Virginia v. Tennessee. His conclusion [was] that the Clause could not be read literally [and this 1893 conclusion has been] approved in subsequent dicta.”
Specifically, the Court’s 1893 ruling in Virginia v. Tennessee stated:
“Looking at the clause in which the terms ‘compact’ or ‘agreement’ appear, it is evident that the prohibition is directed to the formation of any combination tending to the increase of political power in the states, which may encroach upon or interfere with the just supremacy of the United States.”
The state power involved in the National Popular Vote compact is specified in Article II, Section 1, Clause 2 the U.S. Constitution:
“Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors….”
In the 1892 case of McPherson v. Blacker (146 U.S. 1), the Court wrote:
“The appointment and mode of appointment of electors belong exclusively to the states under the constitution of the United States”
The National Popular Vote compact would not “encroach upon or interfere with the just supremacy of the United States” because there is simply no federal power—much less federal supremacy—in the area of awarding of electoral votes in the first place.