TACOMA, Wash. (AP) - Microsoft Corp. and the Seattle Mariners have made big contributions to the campaign for a $17.7 billion road and mass transit measure on the November ballot.

The world's largest software maker has given $200,000 to Keep Washington Rolling, while the Mariners have given $75,000. Construction firms and related companies also have made hefty donations to the campaign, which has raised about $690,000 so far, according to state Public Disclosure Commission records.

Voters in Pierce, King and Snohomish counties will decide on a plan to spend $6.9 billion on road construction and $10.8 billion on mass transit.

The plan would add 50 miles of light rail and help pay for major highway construction projects like expanding Interstate 405 in King County and extending Highway 167 from Puyallup to the Port of Tacoma in Pierce County.

Formal opposition campaigns are still organizing, and critics acknowledge they'll have a hard time matching the money supporters have raised.

"We know this is going to be a close election," said Aaron Toso, a spokesman for Keep Washington Rolling, the campaign supporting the construction plan.

A mix of sales and motor vehicle excise taxes would pay for the plan. Supporters say the road and transit work is needed to address traffic congestion that will only get worse as an estimated 1.2 million people move into the region by 2030.

Other big contributions have come from the National Association of Industrial and Office Properties, PEMCO Mutual Insurance Co. and the Washington Association of Realtors, each of which has donated $50,000.

Representatives of Microsoft did not respond to calls for comment about the company's donation.

Seattle Mariners spokeswoman Rebecca Hale said team surveys show that fans care about transportation.

"On any given game, over half of our fans are coming from outside King County," Hale said. "They're traveling more than an hour to get here."

Hale said the team doesn't endorse particular construction projects but wants to improve regional transportation in general.

"We want our fans to be able to get to the ballpark," she said.

Many contributors to Keep Washington Rolling are in construction and related fields that could benefit from public spending the ballot measure would authorize.

Among them: the Washington State Building and Construction Trades Council ($40,000), the American Council of Engineering Companies ($35,000) and Associated General Contractors of Washington ($20,000).

But Toso said the road and transit package has broad support because it offers a balanced solution to traffic congestion.

"I think people understand we have a transportation problem in this region," Toso said. "All of those groups have a vested interest in ensuring that people and goods and services can move freely throughout the region."

The plan has its critics, however. Some believe it spends too much on light rail instead of road improvements and expanded bus service that serve more people more cheaply.

"Maybe it's a lot nicer to ride on a train than a bus, but is the taxpayer responsible to furnish the commuter a more stylish ride at a significantly greater cost?" said former state Sen. Jim Horn of Mercer Island, chairman of the Eastside Transportation Association.

Others including the Sierra Club say the plan overemphasizes highway construction and will worsen global warming.

Mike O'Brien, chairman of the environmental group's regional chapter, said building and expanding highways isn't a long-term solution to traffic congestion because the new lanes fill up in five to 10 years.

"We're not going to be able to build our way out of this," O'Brien said.

So far, public support for the roads and transit measure is fairly strong, according to pollster Stuart Elway. A poll he conducted in June found 57 percent of respondents supported the measure.

Elway said there was no organized opposition at the time of the poll, so the level of support could change.

No opposition campaign has registered with the Public Disclosure Commission. But O'Brien said he's ready to file paperwork. And a group that wants more highway spending also is preparing to file, The News Tribune of Tacoma reported Sunday.