Topeka ? Democratic congressional challenger Nancy Boyda repeated concerns Wednesday about a proposed multilane superhighway that eventually could span the United States from Mexico to Canada, calling it a threat to Kansans.

“There seems to be a plan to blur the border with the United States and Mexico,” Boyda said, referring to a proposed 10-lane corridor parallel to Interstate 35 in Texas.

Boyda has made the highway an issue in her effort to defeat incumbent Republican Jim Ryun in a rematch of their 2nd District race two years ago. While Ryun says immigration is the top issue on his agenda, Boyda said allowing Texas to “blow a quarter-mile-wide hole in the border” runs afoul with any get-tough talk.

Speaking Wednesday at a candidate forum in Topeka, Ryun dismissed the Texas proposal and fears of a flow of illegal guns, drugs and immigrants as nothing more than a growing conspiracy theory.

“This is definitely based on fiction,” Ryun said. “It is based on an Internet story.”

State and regional highway officials agree, saying there are no grandiose plans to cut a wide swath across the central United States from Laredo, Texas, to Detroit.

Terry Heidner, Kansas Department of Transportation director of planning and development, said any potential for expanding Interstate 35 through Kansas is in the distant future.

“There is a lot of traffic along I-35 and someday we may have to expand the capacity along that corridor,” Heidner said.

For now, he said, there are no plans and no money even if there was talk of a new highway.

“It hasn’t been kept quiet; it’s been kept secret,” Boyda said.

After the forum, Boyda’s staff provided newspaper clippings, brochures and other documents she says illustrate efforts to make the Kansas City area an international trade hub.

She said Ryun and other Republicans “have a hard time explaining how they will improve immigration while this is going on.”

Boyda opposes a proposal by Texas Gov. Rick Perry to build the Trans Texas Corridor, a 10-lane highway that would parallel Interstate 35 through Texas to the Oklahoma border. The $184 billion plan would link rail, truck and automobile traffic heading from Mexico to Canada, following the existing interstates north. Part of the road would be privately maintained through tolls.

Interstate 35, which crosses Kansas for 235 miles from the Oklahoma border to Kansas City, Mo., has been modified to ease congestion and increase safety.

Ryun, seeking his sixth term, said Boyda’s claims are unfounded, though he has voted for spending bills that have included funds for study of the proposed project. Those bills contained money for replacement of a bridge over the Kansas River through Topeka.

Boyda also cited support for the Texas project by North America’s SuperCorridor Coalition Inc., a Dallas-based organization that supports efforts to improve and maintain Interstates 35, 29 and 94 linking Mexico to Canada.

She said although statements on the NASCO Web site claim there is no plan for a superhighway across the nation, support for the Trans Texas Corridor speaks otherwise.

But Tiffany Melvin, NASCO’s executive director, said Boyda has never talked to the group and misrepresents its mission. Melvin said NASCO supports state efforts to maintain and enhance the existing highway system, not push for new miles of asphalt to further the goals of the North American Free Trade Agreement.