WASHINGTON -- Mississippi Republican consultant Austin Barbour will join Mitt Romney's campaign in Boston and will serve as deputy to top Romney adviser Stuart Stevens, The Huffington Post has learned from sources with knowledge of the move.

Barbour has been a national finance chairman for Romney, and helped staff get out the vote efforts in numerous primary states. He also headed up the ground game for Romney in Mississippi, where the former Massachusetts governor came closest to winning a state in the deep South.

Barbour, 36, is a nephew to former Mississippi Gov. Haley Barbour (R), who himself explored a run for president before deciding against it last year. Stevens, who is a native of Mississippi, has a longstanding relationship with the Barbour family.

Austin Barbour was finance chairman for his uncle's gubernatorial campaign in 2003, and then ran Sen. Roger Wicker's (R-Miss.) successful campaign in 2008, in which he defeated former Gov. Ronnie Musgrove (D). Barbour was finance director for the Mississippi Republican Party in 2011 when it won control of the state House for the first time since 1870.

Barbour will move to Boston, allowing Stevens to continue traveling with Romney on the campaign trail while also ensuring that Stevens can remain more plugged in to the decision-making process at Romney headquarters.

The Romney campaign is in the midst of a dramatic expansion in size, now that the Republican nomination is all but in hand and attention has shifted to a general election matchup with President Barack Obama. The Boston Globe reported this week that full-time staff will go from 80 to about 400 in the coming weeks.

Former Bush White House adviser and Republican National Committee Chairman Ed Gillespie was the first big name to officially join Romney's expanding inner circle, coming on earlier this month. Long time Republican strategist Charlie Black was added to Romney's roster of informal and unpaid advisers earlier this year.

Barbour's hiring is the first full-time addition in the current expansion who will be a permanent fixture in the high command in Boston. Rich Beeson, the Romney campaign's political director, and Eric Fehrnstrom, a long time adviser and spokesman, are adding staff to the political and communications shops. It's not clear how many of those jobs will be in Boston as opposed to around the country, as the campaign sets up regional positions and state field offices.

In addition, long-time ad man Jim Ferguson is in Boston and is doing full-time media work for the campaign, as first reported by AdWeek.

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