Fifteen Republican senators sent a letter to the White House Thursday, urging President Barack Obama to withdraw the nomination of former Sen. Chuck Hagel (R-Neb.) for secretary of defense and going as far as stating that a nominee would require 89 votes for confirmation.

The letter was signed by Senate Minority Whip John Cornyn (R-Texas), along with other notable senators including Lindsay Graham (R-S.C.), Ted Cruz (R-Texas), Marco Rubio (R-Fla.) and Jim Inhofe (R-Okla.)

In the letter, the senators call for the president to withdraw the nomination because Hagel does not have "the broad base of bipartisan support and confidence needed to serve efficiently."

The letter came after a key Republican senator, Sen. Richard Shelby (Ala.), announced that he plans to vote for Hagel, making him the third GOP member to announce he would do so.

Notably, Republican Sens. John McCain (Ariz.) and Kelly Ayotte (N.H.), who have both opposed Hagel, did not add their names to the letter.

The letter claims that historically, no secretary of defense nominee has been confirmed with more than 11 opposing votes and calls for a less "controversial" and "divisive" candidate. However, presidential nominations have only required 50 votes for confirmation, and filibustering one, as has happened with the Hagel nomination, is unprecedented.

Despite the move, Republicans have signaled more willingness to consider the Hagel nomination for a full vote after the President's Day Recess.

Read the full letter below:

Letter to President Obama on Hagel Nomination by

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