Home, they say, is where the heart is. But Democrat John Garamendi, the lieutenant governor of California, had unusual leeway in deciding where “home” is, before he announced last week that he plans to run in a pending special House election for the 10th Congressional District seat.

That’s the seat Democratic Rep. Ellen O. Tauscher will soon vacate, assuming the Senate confirms her appointment by President Obama to a State Department post.

Because of a fluke in the congressional redistricting that followed the 2000 census, a congressional district boundary runs right through Garamendi’s property in Walnut Grove, near the state capital of Sacramento.

His front yard is in the 10th District, which spans from the East Bay suburbs of San Francisco to the western suburbs of Sacramento. His house, though, is in the 3rd District, which ranges from suburban Sacramento east through part of the Sierra mountains to the Nevada border, and is represented by veteran Republican officeholder Dan Lungren .

Garamendi had been mulling a bid for governor of California before switching to congressional politics. With a political resume that dates to the mid-1970s and includes previous stints as state assemblyman, state senator, state insurance commissioner and deputy secretary of Interior under President Bill Clinton, he appears a formidable contender.

But some Democratic activists are grumbling over Garamendi’s next step in his political career — not his decision to run for the House, but where.

The Democrats already had experienced and well-known candidates lining up to run in the 10th District, a party stronghold that gave 65 percent of its November 2008 votes both to Obama as the Democratic presidential nominee and Tauscher in her seventh House win — and the last before Obama tapped her to be undersecretary of State for arms control and international security.

State Sen. Mark DeSaulnier was endorsed by Tauscher, a move she made while Garamendi was still was a prospective candidate for governor. State Assemblywoman Joan Buchanan has also declared her intention to run.

Meanwhile, Democratic strategists are in search of a top-tier challenger for the race in the 3rd District, where Lungren won last year by a surprisingly close margin of less than 6 percentage points over little-known opponent Bill Durston. Obama on the same ballot outran Republican presidential nominee John McCain by a half of 1 percentage point, despite the district’s Republican-leaning reputation and the GOP’s 40 percent to 38 percent edge over the Democrats in voter registration.

Democrats, though, could use a candidate with a big name and fundraising prowess to take the fight to Lungren. Garamendi would certainly fill that bill, which is why some of his fellow Democrats are unhappy about his decision to instead run in the 10th.

National Democratic campaign planners say they are resigned to Garamendi’s choice. “We’re sort of in the recruiting stage right now,” said Andy Stone, western regional spokesman for the Democratic Congressional Campaign Committee (DCCC), in reference to the 3rd District contest. Asked if the DCCC had asked Garamendi to reconsider, Stone said, “The lieutenant governor has made his choice, so that’s that.”

The 3rd District is not the obvious choice, at least on paper, for a targeted takeover campaign by the Democrats. Lungren is well-seasoned, as he held a southern California House seat from 1979 to 1989, was state attorney general from 1991 to 1999 (which prompted his relocation to the Sacramento area) and was the unsuccessful Republican nominee for governor in 1998. He returned to the political arena in 2004 when he won a hard-fought primary for an open Republican seat, then easily won the general election that November.

He continued on this roll in 2006, when he first faced a challenge by Democrat Durston, an emergency room physician. Although a growing national anti-Republican trend that year produced big gains that boosted the Democrats into a House majority, Lungren coasted to victory over Dunston by a margin of more than 20 percentage points.