Updated

Seven months after Michigan elected a new governor and legislature, negative TV ads are popping up again — along with fiery speeches, robo-calls and accusations of twisting facts and dirty tricks.

This time, it's not about an election. It's about a bridge.

Government officials and business groups have agreed for years on the need for a second international bridge between Detroit and the Canadian city of Windsor, Ontario, the busiest commercial border crossing in North America. The effort has stalled, largely because of opposition from the owner of the existing Ambassador Bridge, billionaire Manuel "Matty" Moroun.

Nearly 30 percent of the goods sold between the U.S. and Canada are trucked across the Detroit River. Yet there are just two main paths through the bottleneck: an underwater tunnel too cramped for tractor-trailers, and the Ambassador — a 7,500-foot span that opened weeks after the 1929 stock market crash.

Moroun contends a publicly supported bridge would compete unfairly with his own. Bridge supporters say it would relieve congestion and provide an alternative in case the aging Ambassador is disabled. Their push has been gaining traction — largely because Republican Gov. Rick Snyder has championed the project since taking office in January.

The clash is a rarity because the vast majority of international bridges are public infrastructure. And the debate is getting ugly.

Snyder is pushing for quick approval of measures to create a U.S.-Canadian authority to oversee construction of a bridge about two miles south of the Ambassador. Legislative hearings started this week. Moroun and his allies are fighting back, saying an overbearing government is trying to destroy his company with a boondoggle that will cost taxpayers $100 million a year.

"Politicians have a bridge they want to sell you," an announcer says darkly in one TV ad. "A bridge we can't afford, with money we don't have."

Backers of a new bridge dispute the $100 million figure. Snyder insists there's enough traffic for two bridges and he's not picking a fight with Moroun.

"It is not anti-anyone. It is about international trade and job creation," he said.

Supporting the plan are both federal governments and corporate heavyweights including General Motors, Ford, Chrysler, Amway and Kellogg. Organized labor is on board. Both Detroit's Democratic mayor and the Republican executive of adjacent Oakland County favor it.

Democrats in the legislature have long backed the idea, and there are signs that opposition from Republicans who control both chambers may be softening. Some lawmakers do question whether the government should be involved, and whether the state would really be free of costs.

Still, Moroun has considerable influence. His family and employees pumped more than $550,000 into races for state offices in 2009-10, the nonpartisan Michigan Campaign Finance Network says.

Also in his corner is the Michigan chapter of Americans for Prosperity. The right-wing advocacy group has sent mass mailings to districts of wavering GOP legislators, and distributed fake eviction notices in a working-class Detroit neighborhood, warning residents their houses could be seized to make way for the bridge. Moroun has also sued the U.S. and Canadian governments over his proposal to build a twin, private bridge.

Meanwhile, anti-Moroun websites and rallies depict him as a slumlord willing to sacrifice economic growth in the depressed city for fatter profits from tolls and duty-free gasoline sales.

The skirmishes foreshadow a summer battle between Moroun, an 84-year-old trucking magnate, and Snyder, 52, a former executive and venture capitalist.

"Should we roll over and let the government take our business? Nobody would do that," said Moroun's son Matthew, the bridge company's vice chairman. Manuel Moroun became sole owner of the privately built bridge in 1979, spending $30 million.

Pressure for a new bridge has mounted with growth of international commerce, particularly since the North American Free Trade Agreement took effect in 1994. It intensified after the 2001 terrorist attacks, when heightened security caused 12-hour backups on the Ambassador and raised fears it might become a target.

Automakers rely on quick shipments between parts and manufacturing plants on both sides of the border. Ford Motor Co. sends 600 trucks across the bridge daily, said executive chairman Bill Ford Jr.

"We've had holdups on the Ambassador Bridge and it's very costly to all of us," Ford said.

For big semitrailers, the nearest alternative is the Blue Water Bridge about 60 miles away. A ferry service in Detroit also operates for trucks carrying hazardous materials.

Supporters believe the latest plan, called the New International Trade Crossing, is one Michigan can't refuse.

The estimated price of a new bridge, toll and customs plazas, and expressway linkups is nearly $4 billion. Backers say it wouldn't cost financially strapped Michigan a penny. Private investors would finance the bridge itself, and Canada has pledged to cover Michigan's $550 million share of the remaining work, eventually recouping the money from tolls. The Obama administration says the Canadian funding would trigger more than $2 billion in federal grants for transportation projects around Michigan.

Too good to be true, the Morouns say. Traffic on the Ambassador is down 40 percent since 2000, which a study commissioned by their company blames on U.S. automakers' loss of market share and production shifts to Southern states, Mexico and China. Their report says a new bridge would undercut the Ambassador, lose money itself and cost taxpayers $1.5 billion over 20 years.

Supporters reply that bridge crossings have ticked upward as the economy revives and will surge over the long term. U.S.-Canada trade grew 20 percent last year and there's talk of a new international bridge in western New York, said Sandy Baruah, CEO of the Detroit Regional Chamber.

"This is a huge economic opportunity and if we dilly-dally we'll lose out," Baruah said.

While the political and legal debates play out, construction worker Tony Herman was less interested in taking sides than seeing someone — even Moroun — get the project started.

"Whatever's going to create more jobs for my union, I'm for," he said.

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Flesher reported from Mackinac Island and Traverse City. Associated Press writer Tim Martin in Lansing contributed to this report.