Derek S. Hoff, an associate professor of history at Kansas State University, is the author of “The State and the Stork: The Population Debate and Policy Making in U.S. History.”

AS a bipartisan group of senators prepares to release its plan for comprehensive immigration reform, a curious argument is emerging from across the political spectrum: the United States needs immigration to make up for its declining birthrate.

“Over the next three decades, annual population growth for the working-age population will be less than a third of what it was over the last 60 years,” President Obama’s economic adviser Alan B. Krueger told the United States Hispanic Chamber of Commerce in March. “Given current trends, nearly all of the growth of the nation’s working-age population in the next 40 years will be accounted for by immigrants and their children.”

Conservatives, including the anti-tax activist Grover G. Norquist, have embraced the argument. Last week, the American Action Forum, led by the Republican budget expert Douglas Holtz-Eakin, found that immigration legislation could raise the annual rate of economic growth by nearly 1 percentage point, partly because it would help with “low U.S. birthrates.”...