Measure 93, an initiative petition by Bill Sizemore's Oregon Taxpayers Union, requires voter approval of all of all tax and fee increases. It includes a two-year retroactive clause that would take away the 2.5 percentage point increases in Multnomah County's vehicle rental and hotel taxes slated to cover much of the convention center expansion.

Mark Williams, general manager of the Metropolitan Exposition-Recreation Commission, which operates the convention center, says MERC will be ready to start right after the election if Measure 93 does not pass. If it passes, city officials have indicated they would probably place the lodging tax increases on a special-election ballot as early as the following March.

Construction on the project, which would add 180,000 square feet of space and 350 parking spaces to the 11-year-old facility, was to begin next month.