Voting ends later tonight in the US states of Kentucky and Oregon, where voters are casting their ballots in the ongoing race for the Democratic Party's presidential nomination.
The last polling stations in Kentucky were to close at midnight Irish time.
In Oregon, where voting is by mail only, completed ballots had to be dropped off at registration centers by 4am Irish time.
Senator Barack Obama is expected to win Oregon, while Senator Hillary Clinton is tipped to win Kentucky.
But Senator Obama is widely expected to have a majority of pledged delegates following today's primaries.
This means he will have reached a threshold that his campaign has said is the critical measure of the will of the party: winning a majority of the delegates awarded in primaries and caucuses.
To get the nomination, Mr Obama needs the votes of the party's superdelegates, and many of them have indicated they are prepared to wait until the end of the primary season on 3 June before declaring their intentions.
Surveys suggest Senator Clinton's coalition of white, blue-collar, female and older voters will deliver the Kentucky vote to her. The state is known for coal mining, thoroughbred racehorses and bluegrass.
Senator Obama is favoured in Oregon, a sparsely populated, liberal state on the western seaboard.
Senator Obama's campaign says he needs only 16 more pledged delegates to reach a majority, which does not count the nearly 800 superdelegates free to vote for the nominee of their choice.
But Senator Clinton's campaign said such talk was a 'slap in the face' for her millions of supporters and an insult to voters in Puerto Rico, Montana and South Dakota, which have yet to weigh in.
Senator Clinton warned the Illinois senator against premature victory celebrations, even though he leads in total wins, pledged delegates, superdelegates and the popular vote in certified primaries and caucuses.
Speaking to supporters in Kentucky last night, Senator Clinton said: 'This is nowhere near over.'
Mr Obama will be in Iowa today, scene of his first victory in January in the Democratic race, in a sign that he is already looking ahead to November.
Most experts believe only a monumental error by Senator Obama can reverse the daily flow of superdelegates or top party officials towards his campaign.
