What is a recess appointment, and is it a feasible option for Trump if Sessions goes?

Even though Jeff Sessions has indicated he has no intention of leaving his post, President Donald Trump's continued public criticism of his attorney general has raised speculation about whether the president might seek to use his recess appointment authority to replace Sessions without Senate oversight should he resign or be fired.

So how would it work?

If Sessions were to resign or be fired by the president, the Constitution allows for the president to fill the post through a recess appointment if the Senate goes on recess for a period of more than 10 days.

Article II of the U.S. Constitution states that the president can "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."

Under those terms, the president could appoint whomever he wants, with the pick remaining in effect until the end of the Senate's next session -- through Jan. 3, 2019 -- without any need for Senate approval altogether in selecting a new acting attorney general.

It's a prospect so worrisome on Capitol Hill that the Senate is set to block the scenario from presenting itself in the first place by keeping the Senate technically in session through the planned August recess.

Democratic Whip Dick Durbin of Illinois said Tuesday that "we're exploring the ways right now" to keep the Senate formally in session through the August recess, calling the prospect that the president could use the recess to stop the special counsel's investigation into Russia's interference in the 2016 election "unacceptable." While the attorney general has the power to fire a special counsel, Sessions has effectively waived that authority to Deputy Attorney General Rod Rosenstein, due to his recusal from campaign-related investigations.

So how does it work?

Democrats could filibuster the motion to adjourn, so that the Senate would gavel in every three days as a means to keep the Senate formally in session.

It's not a new approach and was used commonly during the previous administration.

Jane Chong, deputy managing editor of the legal blog Lawfare, notes that Sen. Mitch McConnell, R-Ky., did just that while Barack Obama was president.

"Under McConnell we saw the Senate do pro forma sessions specifically to prevent from going into recess under this definition and, by extension, to prevent President Obama from exercising his recess powers," Chong said.

The power to decide whether or not the Senate is in session rests solely with that legislative branch, with Chong pointing to the Supreme Court's ruling in the 2014 National Labor Relations Board v. Noel Canning case.

"We hold that, for purposes of the Recess Appointments Clause, the Senate is in session when it says it is, provided that, under its own rules, it retains the capacity to transact Senate business," the case reads.