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Conference USA was waiting on a decision by Marshall before progressing with potential expansion by as many as four schools to bolster the embattled league, sources told CBS Sports. The Thundering Herd on Friday formally decided to join the Sun Belt, sources told CBS Sports, giving the league clarity on which direction it must head.

There is known mutual interest between Conference USA and both New Mexico State and Liberty, though adding both teams would only bring Conference USA to seven members following Marshall's eventual departure. As such, Conference USA is also considering adding UConn in football only and/or an FCS school to round out the league. Sam Houston from the WAC mentioned as the favorite by one source.

"All eyes are on Marshall. Marshall has a tough decision," said a source intimately involved in the Conference USA discussions before Marshall made its call Friday. "Decide to go to the Sun Belt and be a middle-of-the-pack program in a 14-team league, or stay in Conference USA and be the most tradition-rich program and compete for championships."

Conference USA has lost nine of its 14 teams to the American Athletic Conference (CharlotteFAUNorth TexasRice,  UABUTSA) and Sun Belt (Marshall, Old DominionSouthern Miss). That after the American's to watched three of its top programs (Cincinnati, Houston, UCF) depart for the Big 12 in conference realignment. Texas and Oklahoma deciding to move from the Big 12 to the SEC kicked off this round of realignment.

The Sun Belt this week added Southern Miss and from Conference USA to its current 10-team conference with Marshall's membership pending. FCS power James Madison is also expected to join the Sun Belt after its leadership on Friday approved the school exploring a move to the FBS. CBS Sports reported last week that those four schools were expected to be invited by the Sun Belt as soon as this week. 

"It's not over for us," Sun Belt commissioner Keith Gill told the Washington Post.

UConn is in an "exploratory conversation" about joining Conference USA, according to one report. It has been an independent in football since 2020 after leaving the AAC to rejoin the Big East in basketball. The Athletic reported Thursday that Conference USA was in discussions with New Mexico State, Liberty and UConn.

The ultimate decision on how to backfill Conference USA hinged on Marshall making its decision as it simultaneously welcomed new school president Brad Smith, an alumnus. Smith had to evaluate a possible move to the Sun Belt with the school's board of governors. Located in Huntington, West Virginia, Marshall is a former FCS power. It has been a Conference USA member since 2005.

Conference USA commissioner Judy MacLeod is known to be committed to keeping the league afloat, and she has been working aggressively to do so.

"It's a tough call," said that first source said of Marshall. "A 16-team SEC is one thing. You're going to get multiple bids in every sport. In the Sun Belt, you're probably only going to get one [postseason] bid in every sport. It's not a great scenario."

Liberty and New Mexico State are currently FBS independents. Liberty became a full FBS member with bowl eligibility in 2019. New Mexico State has been an independent since 2018 after spending four years in the Sun Belt, its second stay in the league. The Aggies were a founding member of the Sun Belt as a football conference beginning in 2001 before moving to the WAC from 2005-12.

New Mexico State would be seen as a travel partner in minor sports with UTEP. The schools are approximately 30 miles apart. Marshall and Liberty would integrate geographically with remaining Conference USA members Western Kentucky and Middle Tennessee.

Sam Houston is the defending FCS national champion that has played in eight of the last 10 FCS playoffs and is located in Huntsville, Texas. The school left the Southland and joined the newly formed WAC in July. Sam Houston officials have long desired to move up to FBS, according to FCS sources.