Growth pressure from the south and east may force Pelosi's 8th District to expand across the Golden Gate into Woolsey's turf in Marin, possibly pushing her district eastward into Solano County.

"Some very powerful people are going to try to partition the North Bay," said Assemblyman Jared Huffman, D-San Rafael.

Huffman, who is termed out of the Assembly in 2012, has announced his candidacy for the 6th District seat on the condition that Woolsey retires. Woolsey, a 10-term incumbent, has said she will make her decision in June.

Woolsey and Huffman contend Sonoma and Marin counties are a natural fit.

"Our district makes sense," Woolsey said. "We are the quintessential community of interest."

If Woolsey steps down, however, the interests of Pelosi and other nearby Democrats may trump the idea of maintaining the status quo in the 6th District.

Whether a district can run across a bridge and still be considered contiguous — connected at all points — is uncertain, Barabba said.

"It's not crisply clear what that means," he said. "That's when you have to use judgment."

The future of Thompson's 1st District seems a bit more clear. It has historically been a coastal district, and its population of 704,012 is the closest to the target of all of the state's 53 congressional districts.

Still, there's chance that Thompson's home in St. Helena could be sliced out of his district.

"I'm not going to say anything," he said. "It's out of my hands."