Voters will go to the polls in Nebraska, Oregon and Idaho today. Oregon and Nebraska both host their presidential primary contests, though those races have ceased to get any significant levels of attention now that the GOP race is all but decided. Idaho holds its state and congressional primary, the first closed primary in the state's history.

Here's a list of four things to watch tonight.

Nebraska Senate Primary

The Nebraska Senate race will be a key race for Republicans and Democrats in the fall. Republicans view the state as one of their best chances to pick up a seat from Democrats,  particularly since the retirement announcement of Nebraska's Democratic Sen. Ben Nelson.

Republican and Democratic voters in Nebraska will both select their nominees for the race today. On the Democratic side, Bob Kerrey, the former governor and senator for the state, is considered the likely nominee. The Republican race is  more fluid.

There are three candidates in the Republican race: Jon Bruning, the state's attorney general, Deb Fischer, a state senator, and state treasurer Don Stenberg. Bruning, 43, has long been considered the favorite, but heading into the primary he faces a late in the game surge from Fischer, 61.

Through-out the primary season Fischer had not been seen a strong contender. She did not enjoy the same financial strength or name recognition as Bruning, or the same financial assistance as Stenberg, whose campaign has been aided by large spending from tea party affiliated groups like the Club For Growth and Freedom Works.  Stenberg and Bruning have mostly focused their attacks on one another.

Recently Fischer, who was endorsed by Sarah Palin, has emerged as a strong challenger. Bruning is still considered the likely nominee, but Republican officials say that a Fischer upset is not out of the realm of possibility.

Turnout

Strong turnout is sometimes interpreted as a sign of enthusiasm, as was the case in Wisconsin's primary for their recall election last week. Republicans were heartened by the strong turnout for Gov. Scott Walker, despite the fact that he was already the presumed candidate (after all, he is the one being recalled.)

In Nebraska, turnout will be driven at least to some degree by the senate primary. Nevertheless, strong turnout for either side in Nebraska and Oregon will be likely be interpreted as a sign of enthusiasm about the general election in those states.

 Delegates

At stake in Tuesday's contest are 63 delegates, though the 35 delegates in Nebraska will not actually be awarded until July, as Tuesday's primary is a beauty contest. Mitt Romney has 973 delegates, according to ABC News calculations, a little less than 200 delegates shy of the 1,144 he needs to win his party's nomination.

It is mathematically impossible for Romney to hit 1,144 on Tuesday night. The earliest that can happen is May 29, when Texas holds its primary.

The surprise factor

Last week the primary development which had everyone talking was the surprisingly strong performance of federal inmate Keith Judd in the Democratic presidential primary in West Virginia. Though it was well known that Obama is not exactly popular in the Mountain state, the 40 percent of the vote Judd received still took observers by surprise.

There are no prison inmates on the ballot in Oregon or Nebraska's Democratic primaries, but a surprise factor like a strong performance by "uncommitted" against Obama in Nebraska, or a big turnout in either party's primaries in Oregon, could still emerge. One thing we've learned from this primary season is to expect the unexpected.