An unidentified man smokes medical marijuana at the Cannabis Cafe in Portland, Ore., in 2011. (Rick Bowmer/Associated Press)

Opposition to Oregon’s Measure 91, which would legalize marijuana for recreational use in that state, outweighs support, but by a tiny margin.

A survey of 403 likely voters conducted by Elway Research for the Oregonian and KGW on Sunday and Monday found that 44 percent support the measure, while 46 percent oppose it. Nine percent were either unsure or wouldn’t say, while the margin of error was five percentage points. In other words, marijuana legalization in Oregon appears to be anyone’s game.

Earlier this month, Oregon Public Broadcasting commissioned a poll that found support winning 52 percent to 41 percent. But 7 percent said they were undecided, and the poll had a margin of error of four percentage points. As the Oregonian’s Jeff Mapes points out, though, the polls make different assumptions about the ages of the voting population:

The Oregonian/KGW survey taken by pollster Stuart Elway has a sample showing that 70 percent of the electorate will be aged 51 or older.  The OPB/Fox survey, conducted by DHM Research of Portland, uses slightly different age ranges, but 58 percent of its sample included voters 45 or older.

That’s important because age makes a huge difference in support for marijuana legalization. A September poll found support for the measure beating opposition by the “narrowest and most unreliable of margins”: 44 percent to 40 percent.

Voters will weigh in on legalization in Oregon, Alaska and D.C. on Tuesday.