Tens of thousands of central San Joaquin Valley residents are beginning to get a considerable amount of attention from incumbent lawmakers they've never voted for.

That's because redistricting shook up the political landscape for congressmen, state Assembly members and state senators, who are starting to canvass their new electorates with mailers and visits.

So between now and the June 5 primary, for instance, four-term Rep. Jim Costa, a Fresno Democrat, will be saying hello to northern Valley cities such as Madera, Merced and Los Banos -- while still representing his old congressional district.

On Friday, he spent some time meeting with city council members in Los Banos.

"The district's gotten, for me, a lot bigger," Costa said. "From Arvin in the south to Gustine in the north. Not officially, of course."

It's a similar story for several elected officials at the state and federal levels, who are busy campaigning in what next year will be their new districts, while still serving their existing districts through the end of this year.

In Costa's case, less than 25% of his current 20th Congressional District -- which covers the western half of Fresno County, all of Kings and part of Kern counties -- will be part of his new 16th District, which includes half the city of Fresno, parts of Fresno and Madera counties, and all of Merced County.

"There's a lot of upheaval," said political analyst Tony Quinn, a redistricting expert and former Republican legislative staffer.

It may be most pronounced for a handful of politicians who aren't even running for office this year.

All four of the central San Joaquin Valley's state Senate districts have been reshaped -- but the senators who represent those regions aren't up for re-election until 2014.

So Ceres Republican Anthony Cannella, Bakersfield Democrat Michael Rubio, Bakersfield Republican Jean Fuller and Modesto Republican Tom Berryhill are caught in a bit of redistricting limbo.

Cannella, for instance, will take over a huge chunk of Fresno County and a greater part of Madera County. He is taking more than 95,000 Fresno County residents who used to be part of a district now represented by Rubio.

Quinn and Matt Rexroad, a veteran political consultant and a Yolo County supervisor, both say that legally the state senators will continue to represent the people who elected them until a new election.

But, being human, senators likely will start spending time where they will seek re-election, both Quinn and Rexroad said.

Cannella has wasted no time. Last month, he introduced legislation that would increase penalties for arson attacks like the one that destroyed 14 Harris Farms cattle trucks in January. Harris Farms, based in western Fresno County, isn't part of his current district but will be part of his new district.

Former Assembly Member Sarah Reyes, a Fresno Democrat, went through redistricting after the 2000 census, and she didn't like that elected officials started ignoring parts of their district they no longer would represent, and started paying attention to parts they didn't yet represent.

"The shuffling of the chess pieces through redistricting causes people to be in campaign mode and not dealing with the issues at hand," she said.

Political oddities aside, almost no part of the Valley will escape some sort of change, though some will see more than others.

Madera Ranchos, for instance, will be part of new districts at the Assembly, state Senate and congressional levels. It's a similar story for Three Rivers in Tulare County.