"Congress must focus on the real drivers of our debt and deficits by enacting real, enforceable spending cuts, structurally reforming our entitlement programs to prevent impending insolvency, and enacting pro-growth tax reform that will reduce tax rates for American families and businesses, and make the tax code more simple, efficient and competitive."

A spokesman for Shelby says he is stepping down after serving the six-year maximum as a ranking member allowed by the Republican Senate Conference.

He is the longest-serving current member of the committee, having joined in 1986.

Crapo, 61, has served as a member of the committee since he joined the Senate in 1999.

A spokesman for Shelby says he would "remain on the panel as its senior Republican and continue to be involved in committee matters."

An industry source and a Congressional-staff source say the change had more to do with the decision of Sen. Thad Cochran, R-Miss., ranking Appropriations Committee member, to become the ranking member of the Senate Agriculture Committee.

That left an opening for Shelby to take a position where he could best serve Alabama, the sources said.

 "Sen. Crapo is one of the hardest working and thoughtful members of the Senate," says Jimi Grande, senior vice president of federal and political affairs for the National Association of Mutual Insurance Companies.

Grande says Crapo's vast experience and his commitment to free markets and open competition make him an excellent choice to serve as the ranking member of the Senate Banking Committee.

"I look forward to working with him closely in the coming months as Congress tackles the reauthorization of TRIA as well as myriad other issues that will be facing NAMIC members in 2013," Grande adds.

Ray Lehmann, a fellow at the R Street Institute, a think tank, cautioned that it "will be difficult to replace the depth of knowledge on insurance and financial services issues that Shelby brought to the committee, but Crapo is a veteran member and his staff has always been very interested in ways that market forces can be used to shape a vibrant, competitive private insurance market."