I know when the Senate itself is split, the Vice President will cast the deciding vote. But in committee hearings where they're voting to approve Cabinet positions (Such as a Department of Security nomination) for a confirmation vote, what happens if this vote is split evenly?
While Azor Ahai's answer is correct in general, that ties are usually resolved in the negative, the Senate power-sharing agreements negotiated for the 107th and 117th (current) Congresses, which were both tied 50-50, contained the following provision:
- the Chairman of a full committee may discharge a subcommittee of any Legislative or Executive Calendar item which has not been reported because of a tie vote and place it on the full committee's agenda
Sec. 3. Pursuant to the provisions and exceptions described in sections 1 and 2, the following additional Standing Orders of the Senate shall be in effect for the 117th Congress:
If a committee has not reported out a measure or matter because of a tie vote, then—
(A) the Chairman of the committee shall transmit a notice of a tie vote to the Secretary of the Senate and such notice shall be printed in the Record; and
(B) after such notice of a tie vote has been transmitted, the Majority Leader or the Minority Leader may, only after consultation with the Chairman and Ranking Member of the committee, make a motion to discharge such measure or matter, and time for debate on such motion shall be limited to 4 hours, to be equally divided between the two Leaders or their designees, with no other motions, points of order, or amendments in order: Provided, That following the use or yielding back of time, the Senate vote on the motion to discharge, without any intervening action, motion, or debate, and if agreed to, the measure or matter be placed immediately on the appropriate Calendar.
This means that in practice if a committee vote to confirm a nominee is tied, the nomination can proceed to a vote on the Senate floor. An example of this came on March 3rd 2021, when the Senate Finance Committee produced a tied vote, 14-14, on President Biden's nominee for the Secretary of Health and Human Services, Xavier Becerra. According to Reuters:
The 14-14 party-line vote sent Becerra’s nomination to Senate Majority Leader Chuck Schumer and Senate Republican leader Mitch McConnell for further action. Under new rules to deal with the 50-50 Senate split between the two parties, either can file a motion to bypass a tied committee and bring matters straight to the Senate floor with a separate procedural vote.
Ties are usually resolved in the negative.
From this link on US circuit and district court nominations (PDF).
If a majority of the committee agrees to any one of the motions to report, the nomination moves to the full Senate. Note that, in the event of a tie vote, the nomination fails to be reported by the committee.