WASHINGTON — President Obama is close to a decision on a Supreme Court nominee based purely on qualifications and experience, White House officials insisted on Monday, but the president’s allies said that political considerations — including whether a nominee had an easily defensible record or appeal to Republicans — were clearly part of Mr. Obama’s calculus.

Speculation now centers on three potential nominees, all federal circuit court judges: Sri Srinivasan, 49, who was confirmed in 2013 with a 97-to-0 vote; Merrick B. Garland, 63, a moderate who has been a finalist in Mr. Obama’s previous Supreme Court searches; and Paul J. Watford, 48, a judge on the Ninth Circuit Court of Appeals in California.

In an afternoon conference call on Monday, Mr. Obama’s political director, David Simas, and three former senior White House officials told activists, donors, elected officials and legal experts they were ready with an elaborate campaign plan after Mr. Obama names his choice. The president’s decision is expected this week and could come as early as Tuesday.

Armed with public polling data, Mr. Simas said on the call that the Republicans’ refusal to consider the president’s nominee was “untenable” and was opposed by two-thirds of the public. He said the White House message would be far more effective once Mr. Obama had chosen a nominee with “impeccable credentials,” according to people who dialed in, who insisted on anonymity to discuss the details of a confidential call.