National Republicans are taking the unusual step of picking sides in a competitive Arizona congressional primary, bypassing an anti-immigration conservative to promote a candidate the party contends could win in November.

The National Republican Congressional Committee is spending more than $122,000 on television ads for state Rep. Steve Huffman. The primary is Sept. 12.

Huffman was hand-picked by retiring Rep. Jim Kolbe (news, bio, voting record), a moderate Republican who has held the House seat for 22 years. While Huffman has led the pack in fundraising, there is no clear favorite in the race.

Huffman faces Randy Graf, a conservative former state lawmaker, and Mike Hellon, a former Arizona Republican Party chairman.

The NRCC ad introduces Huffman as "the conservative choice" of the U.S. Chamber of Commerce, a candidate who backs an immigration policy that "puts security first."

It's rare for the national party to take sides in a primary for an open seat. NRCC spokesman Ed Patru said the party has not advertised on behalf of any other GOP primary candidates this year.

Patru would not comment on why the group was advertising on behalf of Huffman.

Graf gave Kolbe a scare in the 2004 primary, losing by just 15 percentage points after accusing Kolbe of being weak on immigration. Immigration has been critical in this year's primary as well, but some party leaders fear Graf's hard-line could cost them the seat in November.

Republicans have only a slight advantage in the district, which includes the Tucson area and spans the southeastern corner of the state.

Rep. John Shadegg (news, bio, voting record), R-Ariz., said in an interview earlier this month that the conventional wisdom in the state is that if Graf wins the nomination, Democrats will have a better chance at winning the seat.

"Kolbe was very moderate and he appealed quite successfully to moderate voters," Shadegg said.

Graf's campaign manager RT Gregg said he's not worried about the NRCC. GOP voters will be "incensed" that national Republicans would try to "dictate how the district should vote," he said Wednesday.