California’s topsy-turvy election system has mashed up with Capitol Hill politics to create this unique phenomenon: On Monday, two out-of-state Republican Senators endorsed a House Democrat running in a new district.

The Senators, John McCain of Arizona and Lindsey Graham of South Carolina, were joined by Independent Sen. Joe Lieberman of Connecticut in throwing their support behind Rep. Howard Berman in his general election race with fellow Democratic Rep. Brad Sherman.

How did this happen?

To start, California’s newly installed independent redistricting commission created a single district in the San Fernando Valley where two seats had existed, pitting Berman and Sherman against one another.

Then, the state’s jungle primary system, which puts the two top vote-getters against one another in the general election, saw the two Democrats advance to compete in November.

“It’s definitely unusual to have Republican Senators endorsing Democratic Members of the House,” veteran California consultant Rose Kapolczynski said. “On the other hand, our new system means in many races there is no Republican running.”

Eight out of the state’s 53 districts feature intraparty races, including the 30th district, where Berman and Sherman were drawn together.

While it was California’s new environment that offered the endorsement opportunity, the decision to do so was born of dynamics on Capitol Hill. The three Senators, who have embraced the nickname “the three amigos,” have long been known for hawkish national security positions, including fervent support of U.S. intervention in Iraq.

Sherman has criticized Berman for his support of military action in Iraq in direct mail, tying Berman to President George W. Bush and saying he “stuck with Bush on the War till the bitter end.” The backing of McCain, Graham and Lieberman is likely because of that policy position, as well as a reward for a Democrat who is willing to work across the aisle on foreign policy.

McCain and Graham have been touring the country to express opposition to upcoming defense budget cutbacks required by the sequestration that takes effect at year’s end.

As for Lieberman, his hawkishness has left him at odds with many Democrats on foreign policy issues, and he no doubt views Berman as one of a dying breed in the party.

“Ideologically, just in pure political science terms, Howard and Brad aren’t really far apart,” Democratic consultant Bill Carrick said. “Where they are different, obviously, is more in terms of their leadership skills and how they function and operate as Members of Congress.”

Berman, the favorite among the California delegation, is at a severe geographic disadvantage against Sherman, who currently represents a little more than half of the electorate expected to vote in November. Berman represents about a quarter, meaning he needs to win over a significant share of voters who have been electing Sherman every two years for more than a decade.

“It is an incredibly complicated political equation,” Carrick said.

The Senators’ endorsements got big play in the district, landing above the fold on the front page of the second section of the Los Angeles Times. It was expected to echo on radio and television throughout the day.

“The question is will Sherman now use this as a new line of attack, somehow undercutting Berman’s progressive credentials?” Democratic consultant Roy Behr asked.

Sherman consultant Parke Skelton was on the phone with Roll Call when he opened up his copy of the Times on Monday morning. “This is going into a mailing. Nice headline,” Skelton said between laughter. “‘Berman to Gain GOP Backing’ – I love it.”

Sherman finished 10 points ahead of Berman in the June primary.

“If you look at the primary results – and I’m sure their polling reflects this – if Howard is going to win and close that gap he has with Brad, he’s going to have to have a pretty good shot in the arm with both Republican voters and also decline-to-state voters,” Carrick said.

Republicans are expected to make up close to a quarter of the vote in November. GOP voters will find two candidates from the other party on the ballot when they enter the polls on Nov. 6, so it’s impossible to tell who they will vote for or whether they will vote at all in that race. Democrats will make up about half of the vote, and independents and decline-to-state voters another quarter.

“This is a brand new system in California,” Kapolczynski said, “and every competitive campaign is trying to figure out how to work within this new framework.”