PORTLAND, Ore. (AP) -- Democrats now make up nearly 42 percent of Oregon voters.

The growth is due to the last-minute voters who flocked to change their party affiliation or register for the first time to participate in the May primary.

The big draw is the presidential contest between Democrats Hillary Clinton and Barack Obama, but plenty of down-ballot races could benefit from the surge in registration.

AP photos

The deadline to register or switch parties was Tuesday.

Ballots will be mailed to voters starting on Friday. Votes are counted May 20th.

According to the secretary of state's office, there were 845,196 registered Democrats in Oregon as of Wednesday, up by nearly 81,000 from January.

During the same period, Republicans lost more than 4,500 voters, according to the secretary of state's count.

There are now 683,371 Republicans registered, or about 33.6 percent of the state's more than 2 million voters.