A "recess appointment" can be made by the president any time Congress is not in session, for any length of time. The person appointed by the president assumes his or her appointed position without the approval of the Senate. The appointee must be approved by the Senate by the end of the next session of Congress, or when the position becomes vacant again.
The power to make recess appointments is granted to the president by Article II, Section 3 of the U.S. Constitution: "The President shall have Power to fill up all Vacancies that may happen during the Recess of the Senate, by granting Commissions which shall expire at the End of their next Session."
While the intent of the Founding Fathers in Article II, Section 3 was to grant the president the power to fill vacancies that actually occurred during a Senate recess, presidents have traditionally applied a much more liberal interpretation, using the clause as a means of bypassing Senate opposition to controversial nominees. Presidents often hope that opposition to their recess nominees will have lessened by the end of the next congressional session. However, recess appointments are more often looked on as a "subterfuge" and tend to harden the attitude of the opposition party, making final confirmation even more unlikely.
President George W. Bush has placed several judges on U.S. courts of appeals via recess appointments when Senate Democrats filibustered their confirmation proceedings. In one controversial case, Judge Charles Pickering, appointed to the Fifth Circuit U.S. Court of Appeals, chose to withdraw his name from consideration for re-nomination when his recess appointment expired. President Bush also appointed Judge William H. Pryor, Jr. to the bench of the Eleventh Circuit Court during a recess, after the Senate repeatedly failed to vote on Pryor's nomination.
President Bill Clinton was harshly criticized for his recess appointment of Bill Lan Lee as assistant attorney general for civil rights, when it became clear that Lee's strong support of affirmative action would lead to Senate opposition.
President Kennedy appointed renowned jurist Thurgood Marshall to the Supreme Court during a Senate recess after Southern senators threatened to block his nomination. Marshall was later confirmed by the full Senate after the end of his "replacement" term.
The Constitution does not specify a minimum length of time the Senate must be in recess before the president can enact a recess appointment. President Theodore Roosevelt was one of the most liberal of all recess appointers, making several appointments during one-day Senate recesses.