Three of the Republicans who helped write the Senate immigration reform bill last year warned President Obama on Thursday not to issue an executive action after the midterm elections.

In a letter to President Obama, Sens. John McCainJohn Sidney McCainSenate's defense authorization would set cyber doctrine Senate Dems hold floor talk-a-thon against latest ObamaCare repeal bill Overnight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions MORE (R-Ariz.), Lindsey GrahamLindsey Olin GrahamTop Louisiana health official rips Cassidy over ObamaCare repeal bill Senate Dems hold floor talk-a-thon against latest ObamaCare repeal bill Overnight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions MORE (R-S.C.) and Marco RubioMarco Antonio RubioOvernight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions Senate passes 0B defense bill Trump bets base will stick with him on immigration MORE (R-Fla.) said that such a move would poison the well for an immigration overhaul. 

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"In this regard, acting by executive order on an issue of this magnitude would be the most divisive action you could take — completely undermining any good-faith effort to meaningfully address this important issue, which would be a disservice to the needs of the American people," they added.

If Obama did take executive action, the components seem likely to include allowing new work permits and expanding ways for immigrants in the U.S. illegally to stay. The three senators argued that bypassing Congress through an executive action would violate the constitutional system of checks and balances.

"Taking executive action along the lines that have been reported would flaunt [sic] the separation of powers and our system of checks and balances, undermine the rule of law, and frustrate the proper administration of our current immigration system," they wrote.

But McCain, Graham, and Rubio maintained that Congress should take its own action on the topic.

"Congress must fulfill its obligations under the Constitution and address this issue," they wrote.

Some pro-reform Republicans have indicated that the party could consider an immigration overhaul if it wins control of the Senate. But Democrats are skeptical the GOP could move such a measure through both chambers, especially when a presidential election year is on the horizon.