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Forty-three Republican senators signed on to a new Supreme Court filing accusing President Obama of grossly overstepping his executive power when he created programs to prevent the deportation of millions of undocumented immigrants. Just as interesting are some of the 11 senators who did not sign on to the politically charged legal document.

Four of the 11 whose signatures were not on the court brief, which declared the president guilty of an “extra-constitutional assertion of a unilateral executive power,” are considered among the most vulnerable Senate Republicans of this election cycle: Kelly Ayotte of New Hampshire, Mark S. Kirk of Illinois, Rob Portman of Ohio and Patrick J. Toomey of Pennsylvania. Two of the others — Richard M. Burr of North Carolina and Lisa Murkowski of Alaska — are also on the ballot this year. Two others — Cory Gardner of Colorado and Dean Heller of Nevada — are from states with large Hispanic populations.

But some of those who did not sign advised against making too much of the decision and expressed their strong support for overturning the president’s actions through the legal system.

“Senator Ayotte has been clear that she strongly opposes the president’s unilateral executive actions on immigration and that she supports challenging them through the court system,” said her spokeswoman Liz Johnson.

Kevin Smith, a spokesman for Mr. Portman, said, “Senator Portman believes the president’s unilateral executive action on immigration violated federal law and exceeded his authority under the Constitution and trusts that Supreme Court will affirm the decision of the Fifth Circuit striking it down.”

Senator Mitch McConnell, the Kentucky Republican and majority leader, led the charge for the court filing, and he is at the head of the list of senators followed by John Cornyn and Ted Cruz, both Republicans of Texas, where a federal judge first ruled that the president’s actions were unconstitutional.