By Stephen Collinson CNN

(CNN) -- Hillary Clinton and Bernie Sanders are in a tight battle to win the Kentucky Democratic primary.

Clinton went into the night looking for a strong win in Kentucky following several recent losses to Sanders. Even if she pulls out a win in the state, the night likely won't be a clean sweep for Clinton as Sanders is poised for victory in the Oregon Democratic primary.

Tuesday's contests aren't likely to change the overall dynamics of the race. Clinton maintains a sizable delegate lead and is poised to become the presumptive Democratic nominee in early June when the final round of states vote.

But her inability to snuff out the Sanders challenge has underscored concerns about her skills on the campaign trail and raised questions about whether the party will unite behind Clinton when she takes on presumptive Republican nominee Donald Trump in the fall.

Trump taunted Clinton about the closeness of the Kentucky race.

"Do you think Crooked Hillary will finally close the deal?" Trump tweeted. "If she can't win Kentucky, she should drop out of race. System rigged!"

Sanders' campaign manager Jeff Weaver told CNN that the close race in Kentucky was a sign that a lot of Democrats "are having second thoughts" about Clinton. "The media is ready to call this race over, but I think voters in the various states want to see this race go on."

Fears that it will be difficult to unify the party after the divisive primary race were exacerbated on Tuesday over claims that Sanders' supporters were violent and abusive in shutting down the Nevada State Democratic Convention on Saturday. Sanders accused party leaders of subverting a fair and transparent process while prominent some Democrats, including Senate Minority Leader Harry Reid, blasted the Vermont senator's response to the uproar.

Kentucky is Clinton's best hope to recast the narrative about her tough month. Polling in the state is sparse, but Clinton has devoted substantial time and resources in the state over the past few days.

The Kentucky and Oregon contests come with Clinton in a strange kind of limbo -- she is almost certain to win the nomination due to her lead of nearly 300 pledged delegates over Sanders, but he is still drawing huge crowds and vowing to fight on, delaying the party's process of uniting behind its nominee.

The former secretary of state is effectively fighting a two-front war, against both Sanders and Trump, who is already turning his full, scorching attention on his likely Democratic rival.

Clinton and her allies seem especially eager to move on to the general election phase of the campaign. Priorities USA, the pro-Clinton super PAC, will begin airing general election ads against Trump on Wednesday in states that will be key battle grounds in November, including Ohio, Florida, Virginia and Nevada.

But first, Clinton must finish the primaries.

Kentucky ought to be the kind of state where she can prosper. Only Democratic voters can take part in its closed primary, meaning independents who normally lean towards Sanders are left out.

Former President Bill Clinton, who campaigned energetically for his wife, carried Kentucky in both his election wins in 1992 and 1996 and the Clintons maintain deep political roots in the state. Clinton has also done well in southern contests during the primary season.

But her comments in a CNN town hall meeting in Ohio in March that her clean energy policies would "put a lot of coal miners and coal companies out of business" stung in a state with a rich mining heritage. Those remarks contributed to a stinging loss for Clinton in last week's West Virginia primary.

In her Kentucky campaign stops, she has lauded the sacrifices of miners and in a bid to court blue collar workers. She also praised President Barack Obama's auto industry bailout while accusing Sanders of opposing the measure, which was important for Kentucky because it is a hub of suppliers for auto manufacturers.

"Here's my thinking, everybody was going down, the last thing we needed was to allow the auto industry with millions of jobs in the supply chain to go down too," Clinton said in Kentucky on Monday.

The Sanders campaign has repeatedly accused Clinton of twisting the truth on the vote, saying the Vermont senator backed the bailout but voted against a bill in which funds for it were contained in a large Wall Street rescue.

Clinton also headlined 11 campaign stops over the last two weeks in Kentucky.

Out west, Oregon's coalition of white, liberal voters is the perfect demographic match for Sanders so he is favored to win the state. Still, voting, which is conducted by mail in Oregon, is only open to registered Democrats -- a factor that could help Clinton.

Kentucky has 55 pledged delegates up for grabs and Oregon has 61 and they are distributed on a proportional basis, meaning that Sanders would need blowout victories to make a meaningful impression on Clinton's pledged delegate advantage.

According to CNN's latest estimates, Clinton has 2,243 delegates including 1,722 pledged delegates and 521 superdelegates -- party officials and office holders who can vote however they choose at the convention.

Sanders has 1,465 delegates, including 1,424 pledged delegates and 41 superdelegates. A total of 2,383 delegates are needed to clinch the Democratic nomination.

Republicans are also voting in Oregon though the contest is largely moot given Trump's status as the presumptive nominee. Still, the primary is likely to bring the billionaire ever closer to the 1,237 delegates he needs to formally clinch the nomination. Currently, Trump has 1,157 delegates. There are 28 Republican delegates up for grabs Tuesday.

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