WASHINGTON (Reuters)  The top Republican on the Senate banking panel made clear Tuesday that he still opposed the nomination of the M.I.T. professor and Nobel laureate, Peter A. Diamond, to the Federal Reserve calling him an “old-fashioned” Keynesian supporter of big government.

Opposition from Senator Richard C. Shelby of Alabama to a nomination that Republicans have already scuttled twice poses a challenge to President Obama, who must decide how much political capital he wants to spend to push for Mr. Diamond’s approval.

“It is clear to many of us that he does not possess the appropriate background, experience or policy preferences to serve,” on the Fed’s board, Mr. Shelby said of Mr. Diamond.

Mr. Diamond won approval from the banking panel twice last year  both on party-line 16-7 votes  but Republicans blocked his consideration by the full Senate, which is needed before he can take a seat on the seven-member board.