OREGON CITY -- Clackamas County voters convincingly approved

, partial returns indicate.

.

"What a clear mandate," Jim Knapp, the original chief sponsor of the initiative measure, said shortly after the results posted.

requires countywide voter approval before officials can spend money to finance, design, construct or operate any rail lines in the county. Generally, opponents of the Portland-Milwaukie light rail extension support the measure, and light rail supporters oppose the measure.

as of Tuesday afternoon, according to the Clackamas County Elections Office.

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It's unclear what effect the measure will have on the under-construction Orange Line, the Portland-to-Milwaukie project at the heart of the controversy. County commissioners obtained a private loan Friday from Bank of America to pay TriMet its $19.9 million tab for the $1.5 billion project. Rail opponents are considering challenging the loan in the courts.

The measure will likely limit Clackamas County's involvement in future rail developments, including high-speed passenger rail service between Seattle and Eugene that is in early stages of discussion.

In King City, the similar Measure 34-199 passed 59 to 41 percent, partial returns indicated.

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