U.S. Treasury Secretary mentioned many strong candidates for Fed chair, with the selection process starting this fall.  
Reports say Trump may nominate a successor earlier to limit Powell's influence, possibly by September or October.  
Potential picks include ex-Fed member Kevin Warsh and White House economic advisor Kevin Hassett.  
Others in the mix: ex-World Bank chief Malpass, Fed governor Waller, and even Treasury Secretary herself.  
Trump's frustration with Powell could speed up the deci