USA Today reports:

Nearly 570,000 people — or 28% of the state’s registered voters — already have cast ballots, says Scott Moore, spokesman for the Oregon Secretary of State’s office. That’s more than half of the nearly 860,000 people who voted in the 2004 primary.

Voter registration also has jumped. Since January, more than 75,000 people registered to vote, nearly 4% of all voters.

In addition, about 90,000 voters changed their party affiliation this year. More than eight in 10 of those party switchers migrated to the Democratic Party — a sign of the heightened interest in the nomination battle between senators Hillary Rodham Clinton and Barack Obama. (There is a Republican primary in the state Tuesday as well, though Sen. John McCain has already wrapped up the party’s nomination.)

Oregon is the only state where no one actually goes to a polling place to vote. Residents vote by mail or drop the ballots off at designated collection spots, including the election offices in each of the state’s 36 counties. Ballots must be received by 8 p.m. local time Tuesday. Note: That’s “received by.” Postmarks don’t count.

Does all this early voting mean that election officials have started counting?

No, says Moore. State law bars workers from starting the tally until Tuesday morning. No results will be released until after 8 p.m. Pacific time.

The state uses paper ballots, which are run through optical scanning machines. Despite that, Moore says election officials generally have more than half the votes tallied by 8 p.m.

Kentucky, which also votes Tuesday, doesn’t have a similar early voting system. About 20,000 people already have voted absentee, says Les Fugate, spokesman for the Kentucky Secretary of State’s office. The Bluegrass State has not seen a big increase in voter registration, he says.