The president, as he has in the past, reiterated that it was “an embarrassment” that women on average earn 77 cents for every dollar men make. But he made no mention of a recent study that found that women in his own White House make 88 cents for every dollar men do. Aides have said women earn the same salary as men of the same rank but that there are more women in lower-paying jobs — an explanation similar to that often given by private-sector employers.

Some critics have said both of those statistics are misleading because they are averages of all men and women in all jobs, rather than apples-to-apples comparisons of men and women in equivalent jobs with equivalent experience. Once such factors are taken into account, they say, the gap is smaller.

“We all support equal pay for equal work and know there’s a problem that must be addressed,” said Kirsten Kukowski, national press secretary for the Republican National Committee. “But many are questioning the Democrats’ motives as they continue their dishonesty about the issue and their own gender gap.”

The Senate is set to vote on the Paycheck Fairness Act on Wednesday, and a memo distributed by the Republican National Committee and two other party committees ahead of the vote noted that it was already illegal to discriminate on the basis of gender. It said Democrats “always seem to wait for an election year to push another empty promise.”

The committees released statistics showing pay gaps in the office staffs of several Democrats up for re-election this year, including Senators Mark Begich of Alaska, Mark R. Warner of Virginia, Mary L. Landrieu of Louisiana and Kay Hagan of North Carolina.