TUSCALOOSA, Ala.  He has made millions as a title insurance executive, landlord and real estate developer in this college town, where the economy, despite trouble nationwide, is still growing nicely. Now, as a United States senator, with the mortgage mess fueling a national economic slowdown, Richard C. Shelby has more say over the revamping of housing finance laws than almost anyone else in Congress.

Mr. Shelby, 74, does not run a key Congressional committee. Instead, as the ranking Republican on the Senate Banking Committee, he is using his clout and the Democrats’ slim majority in the Senate to help determine what gets in, or almost as important, what is left out, of legislation.

He will soon play a major role in deciding the fate of one such bill, to help struggling homeowners, that the House passed, 266 to 154, on Thursday.

But over the years, his critics say, Mr. Shelby’s ties to the mortgage industry and the Alabama real estate market, and the generous campaign donations he receives from financial services companies, have distorted his perspective and led him to delay critical legislative remedies.