WASHINGTON — The wall of Republican opposition to the nomination of Judge Merrick B. Garland to the Supreme Court has been shored up by two Republican senators revoking their support for holding confirmation hearings.

Their moves highlight the immense pressure that Republican leaders are placing on senators as they try to build unified opposition to President Obama’s choice to replace Justice Antonin Scalia, who died in February.

As the White House heralds the growing number of Republicans agreeing to meet with Judge Garland, Senators Jerry Moran of Kansas and Lisa Murkowski of Alaska have reversed themselves and say they now back the decision made by Senator Charles E. Grassley of Iowa, chairman of the Judiciary Committee, not to hold hearings.

“Senator Moran called Senator Grassley to discuss his position,” said a statement released by Mr. Moran’s office on Friday. “As Senator Moran has said, he is opposed to President Obama’s Supreme Court nominee. He has examined Judge Garland’s record and didn’t need hearings to conclude that the nominee’s judicial philosophy, disregard for Second Amendment rights and sympathy for federal government bureaucracy make Garland unacceptable to serve on the Supreme Court.”