Several Republican senators expressed shock on Wednesday when Donald Trump announced he would nominate Matt Gaetz, the hard-right congressman known for instigating fights with members of his own party, as attorney general.

“The president obviously has the right to nominate whomever he wants, but I think this is an example of why it’s so important that we have the advice and consent provisions in the constitution,” the Republican senator Susan Collins of Maine told reporters on Wednesday. “I’m sure that there will be many, many questions raised at Mr Gaetz’s hearing, if in fact the nomination goes forward.”

But the president-elect has proposed an archaic and in recent years little-used mechanism to get his nominees installed without Senate confirmation: recess appointments.

“Any Republican Senator seeking the coveted LEADERSHIP position in the United States Senate must agree to Recess Appointments (in the Senate!), without which we will not be able to get people confirmed in a timely manner,” Trump said on Sunday. “We need positions filled IMMEDIATELY!”

If Trump pursues a strategy of recess appointments, it could severely curtail the Senate’s power to serve as a check on the new president’s nominations and allow controversial picks such as Gaetz to move forward.

Here’s everything to know about recess appointments:

What does the constitution say about Senate confirmation of presidential nominations?

Article 2, section 2 of the US constitution states that the president “shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States”.

Hundreds of senior officials in the federal government, including all members of the president’s cabinet, are subject to Senate approval, meaning they need the support of at least 51 members of the upper chamber to be confirmed.

How do recess appointments allow a president to circumvent the Senate confirmation process?

Although the US constitution outlines how the Senate serves as a check on presidential nominations, it also provides an alternate route for installing officials who are usually subject to the confirmation process.

Article 2, section 2 further states that 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”.

This allows the president to install nominees in posts that might otherwise go vacant while the Senate is out of session. If Trump were to utilize recess appointments at the start of his term, those appointees could stay in their posts until the end of the next Senate session, or until the end of 2026.

Why do recess appointments exist?

Recess appointments have been criticized as an anachronism dating back to the country’s founding, when Congress was in session much less frequently than it is now and correspondence over an important vacancy in the federal government could take weeks.

Today, when instant communication and airplane travel are the norm, the idea that the president may need to rely on recess appointments to fill key government posts appears absurd, sparking intense criticism of the practice in recent years.

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Have other recent presidents relied on recess appointments?

According to the Congressional Research Service, Bill Clinton made 139 recess appointments, while George W Bush made 171 recess appointments. But Barack Obama only made 32 recess appointments, as the supreme court issued a critical ruling on the practice during his presidency.

In its 2014 decision of NLRB v Noel Canning, the court ruled that several of Obama’s recess appointments had violated the constitution because the Senate was not out of session long enough to merit those appointments. The court noted that a Senate recess of at least 10 days is required to allow for recess appointments.

In recent years, particularly when the Senate and the White House have been controlled by opposing parties, Senate majority leaders have relied on pro forma sessions, in which no real congressional business is conducted, to limit recesses. For that reason, neither Trump nor Biden had any recess appointments.

Would Senate Republicans allow Trump to use recess appointments for his cabinet nominees?

That remains unclear, although the newly elected Senate majority leader, Republican John Thune of South Dakota, has suggested he is open to the idea.

“We must act quickly and decisively to get the president’s nominees in place as soon as possible, [and] all options are on the table to make that happen, including recess appointments,” Thune said on Sunday. “We cannot let Schumer and Senate [Democrats] block the will of the American people.”

Senate Democrats could attempt to at least slow the recess appointment process by holding a vote-a-rama, a tedious and lengthy procedure that could force the chamber to stay in session, but such tactics are unlikely to change the final outcome when Republicans hold a 53-47 majority.

If Thune did clear the way for recess appointments, he could significantly damage one of the Senate’s most important functions at a time when his party has just won a governing trifecta in Washington. Such a decision would only further underscore the iron grip Trump has over the Republican party.