The Texas state director of Republican presidential hopeful Jeb Bush's young donor program has quit and is planning to join the campaign of Democrat Martin O'Malley.

Shooter Russell, a University of Texas sophomore who since June had held the formal role with Bush's "Mission: NEXT program," told the Houston Chronicle he made the switch because of the GOP's opposition to people fleeing war-torn Syria.

"The final nail in the coffin were Trump's comments on Muslims, the inaction by the party, and our very own state's actions on blocking Syrian refugees," said Russell, who added that he has cousins who do mission work in the Middle East.

As state director, Russell said he oversaw about 80 volunteers at 15 chapters across the state, set up phone-banking plans and helped organize an event featuring Bush's son, Texas Land Commissioner George P. Bush. Now, he said, he is planning to travel to Iowa to campaign for O'Malley, a former governor of Maryland who is far behind in the polls.

The abrupt change in loyalty may invite comparisons to CJ Pearson, the YouTube star from Texas who endorsed GOP U.S. Sens. Ted Cruz and Rand Paul before recently announcing his support for Democrat Bernie Sanders. Russell had a more formal role with the Bush campaign than Pearson had with Cruz or Paul, however.

The defection is the latest sign of the troubled campaign of Bush, a former governor of Florida and son and brother of presidents. Bush was the early front-runner for the nomination, but has struggled. A recent poll in his home state of Texas put his support at 4 percent.

The campaign did not return a message seeking comment.