Some 2.5 million illegal immigrants have flowed into the United States under President Obama, with 790,000 rushing in since 2013, according to a new analysis.

Calculations from the Center for Migration Studies and the Pew Research Center indicate 1.5 to 1.7 million aliens joined the illegal population from 2009 to 2013 — either overstaying a temporary visa or sneaking into the country, according to a Center for Immigration Studies report out Monday morning.

The immigration watchdog's analysis of Census Bureau data also showed that an additional 790,000 illegals entered from the middle of 2013 to May of 2015, for a total of 2.5 million new illegal immigrants since Obama took office in January of 2009. That is a rate of 300,000 to 400,000 a year.

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Illegal immigrants caught at the U.S.-Mexico border. AP Photo

The issue has become explosive under Obama, especially in the last year when tens of thousands of children and young adults joined the regular flow of illegals from Latin America.

It has also embroiled the GOP presidential contest, with Donald Trump blasting Mexico and party leaders worrying about image of Republicans.

But the CIS report written by Steven A. Camarota, director of research, found that illegal immigration was higher under former President George W. Bush, potentially undermining the GOP's bid to sound tough on the issue. Under Bush, 500,000-600,000 illegals surged in a year.

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Also, the report found that the overall population of illegals has remained "roughly constant," indicating that the surge in of immigrants is balanced by those going home or getting legal status.

Immigration has become a presidential campaign issue. AP Photo

Other points in the CIS report released Monday:

— Had the United States not allowed so many new illegal immigrants to settle in the country since 2009, the total number of illegal immigrants would have fallen by 2.5 million. But the arrival of so many new illegal immigrants offset this attrition in the illegal population.

— While the level of new illegal immigration is lower than a decade ago, the enormous ongoing scale of illegal immigration is a clear indication that the United States has not come close to controlling it.

— Prior research indicates that roughly half a million illegal immigrants return home on their own each year, are deported, die, or get permanent residence. Those who get legal status each year are not beneficiaries of the president's administrative amnesty known as DACA — which does not give permanent residence, but does provide Social Security numbers, work authorization, and identity documents. Rather it has been long-standing policy to allow those who violate immigration laws to still get green cards (permanent residency) if they qualify in one of the legal immigration categories such as marrying a U.S. citizen.

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Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.