A Senate committee approved his nomination on Wednesday, but two Republican senators have vowed to block it.
By contrast, several senators had vowed to fight the nomination of Mr. Babbitt.
Some senators vowed they would wage a floor fight on Sunday to save part of the program.
But senators opposed to the bases vowed to block its passage, calling it illegal.
But the biotechnology and pharmaceutical industries have objected to the patent extension, and one senator has vowed to try to kill it on the Senate floor.
Several senators had vowed to hold up Dr. McClellan's confirmation until he testified on drug imports.
More than 60 senators have already vowed to support him, and the leaders of both parties said they expected to hold the full vote on Tuesday.
Republican senators on the committee vowed to try to change the bill when it reaches the Senate floor.
The senator, who faces re-election this year, had vowed to run regardless of the inquiry's outcome.
But before the nominee could be introduced, the two Democratic senators from Maryland vowed he would never be confirmed.