WASHINGTON — Washington Republican Rep. Dave Reichert is again trying to expand the Alpine Lakes Wilderness area east of Seattle.

But this time he has an important Democratic ally: Sen. Patty Murray, D-Wash., signed on Thursday as a co-sponsor of the bill and said she would lead efforts in the Senate.

At a joint news conference Thursday, Reichert and Murray told reporters the bill was an opportunity to preserve an important part of Washington state for future generations.

The proposal would expand the wilderness area in the central Cascade Range by about 22,000 acres, and designate parts of the Pratt River and Middle Fork Snoqualmie River as wild and scenic.

Murray said she grew up hiking and camping in Washington and wants to make sure her 8-year-old grandson can do the same.

“I want to leave the same kind of legacy for my grandson and for future generations to enjoy,” she said.

Reichert said the bipartisan bill, introduced Thursday in the House and Senate, would “carry on the great Washington state conservation tradition of working together to preserve our natural resources for our children and grandchildren.” Reichert offered a similar bill in the last Congress.

Sen. Maria Cantwell, D-Wash., and Washington Democratic Reps. Jim McDermott, Adam Smith, Jay Inslee and Brian Baird all support the new bill, Reichert and Murray said. Rep. Norm Dicks, D-Wash., who supported the previous Alpine Lakes bill, has not signed on as a co-sponsor of the new measure, said Reichert spokeswoman Abigail Shilling.

All the bipartisan talk Thursday masked an unspoken reality: Reichert is considered by many state and national Republicans as the party’s leading choice to challenge Murray for her Senate seat next year.

Neither lawmaker mentioned the possible rivalry at a conference call with reporters, and their representatives downplayed the idea Thursday.

“We’re not focused on that. We’re focused on getting this done for the people of Washington state,” said Alex Glass, Murray’s spokeswoman.

Shilling, Reichert’s spokeswoman, used similar language in a separate interview.

“I would say right now he’s focused on the job he’s doing,” Shilling said of her boss, adding that Reichert has no timetable for when he might decide on a Senate race.

The proposed bill includes land in the 2nd Congressional District. Rep. Rick Larsen, D-Wash., who represents the district, is not among the bill’s co-sponsors.

Larsen, who worked with Murray on the successful bill to create the Wild Sky Wilderness nearby in the Cascades, was “well aware” of the Alpine Lakes bill and has been working with her and others on it, Murray said.

Larsen could not be reached for comment Thursday.