Hillary Clinton continues to move ever closer to clinching the Democratic nomination with each successive primary contest but Bernie Sanders could get more victories in his column on Tuesday when voters in Kentucky and Oregon head to the polls.
Oregon is the kind of progressive, activist state where Sanders and his kind of politics have long been popular. Clinton easily won Kentucky during the 2008 primaries, and it was expected at the start of this campaign that she would run ahead of the socialist Sanders in areas where Democrats are more conservative.
But Sanders' victories earlier this month in Indiana and West Virginia, states that border Kentucky, suggest he could do very well in the Bluegrass State as well. Here are some key things to watch for Tuesday:
Sanders' Advantage: Oregon and Kentucky Have Small Populations of People of Color
Black voters have overwhelmingly backed Clinton during the primary season, and her performance in most states has been directly correlated to their African-American populations. So Kentucky and Oregon present big challenges for Clinton.
Nationally, African-Americans are 13 percent of the population. They are just 2 percent in Oregon, and 8 percent in Kentucky. (In this sense, Kentucky, while generally defined as in the South, is distinct from that region. The black population in neighboring Tennessee, where Clinton won, is 17 percent.)
Latinos (17 percent of the U.S. population) have generally favored Clinton as well, and they are only 3 percent of the population in Kentucky.
Eastern Kentucky Could Be Tough for Clinton
In the 2008 Democratic primary, Clinton won 118 of Kentucky's 120 counties, getting 65 percent of the vote statewide, compared to Barack Obama's 30 percent. In Kentucky's Fifth Congressional District, the area where much of the state's coal industry is based, Clinton won about 88 percent of the vote.
But that result may mean nothing now. Clinton also blew out Obama in neighboring West Virginia in 2008, only to lose resoundingly to Sanders in the primary there last week.
Many of the counties in Eastern Kentucky are part of coal country and have similar demographics to West Virginia: few college graduates, small black populations, high poverty rates, and declining economies. If the pattern from West Virginia holds, Sanders will be very strong in this region.
This area is also where Clinton's controversial remarks about coal are likely to be most problematic.
In a town hall in Ohio in March, Clinton said, "I'm the only candidate which has a policy about how to bring economic opportunity using clean renewable energy as the key into coal country. Because we're going to put a lot of coal miners and coal companies out of business … And we're going to make it clear that we don't want to forget those people. Those people labored in those mines for generations, losing their health, often losing their lives to turn on our lights and power our factories."
And in this region, running as the successor to Obama is not helpful to Clinton. In many counties in Eastern Kentucky, Obama won less than 20 percent of the vote in 2012. Many voters in Eastern Kentucky view the president as having waged a "war on coal."
Clinton and Sanders are both running as environmentalist candidates. They support the Obama administration's moves to impose tougher emissions regulations on coal plants and to encourage the use of natural gas, solar and wind power instead of coal. Sanders regularly describes himself as more committed to fighting climate change than Clinton.
But conservative Democrats in West Virginia favored the socialist Sanders over Clinton, a pattern that could be repeated in Kentucky.
Clinton Could Win Louisville and Lexington and Still Lose
Jefferson County, which includes Louisville, and Fayette County, which includes Lexington, are areas Obama won in the 2008 primary and in the general election in 2008 and 2012.
More importantly, for this primary, Jefferson County is 22 percent black, Fayette 15 percent. That is likely why Clinton spent Sunday morning at two of Louisville's largest black churches.
That said, those cities are part of a general pattern of metropolitan areas, like Charlotte and Birmingham, increasingly moving left. Louisville congressman John Yarmuth is backing Clinton, but his politics are in many ways closer to Sanders'. Activists in Louisville successfully pushed for an increase in the city's minimum wage in 2014, and Lexington followed suit last year.
So Sanders is likely to do well in Louisville, particularly among its white voters.
And the Vermont senator can win Kentucky if he loses those two big countries narrowly and carries the more rural areas of the state. This is how Sanders won nearby Indiana, even as Clinton defeated him Indianapolis.
About 3 million of Kentucky's 4 million residents live outside of Louisville and Lexington.
The Closed Primary Could Help Clinton
Kentucky's primary, unlike West Virginia's, is only open to registered Democrats. In most states during the Democratic primary, that has been an advantage for Clinton, because Sanders tends to be stronger among voters who are independents.
But Kentucky's Democrats are not like those nationally. The state, like many in the South, was controlled by Democrats for decades. So many Kentuckians remain registered Democrats and might back a Democratic candidate in a state or local race, but favor Republicans at the federal level. The number of registered Democrats in the state (1.7 million) is higher than the number of registered Republicans (1.3 million) even though Mitt Romney won Kentucky by 23 percent in 2012.
Like in West Virginia, some voters in this Democratic primary could be people who back Donald Trump in November.
Is Kentucky More Like Indiana, Tennessee or West Virginia?
Clinton easily won (66 percent to 32 percent) the March primary in Tennessee, another state bordering Kentucky. And according to exit polls, she won both the white (57 percent of the vote to Clinton) and black (89 percent) electorates in that state. She carried the state's rural and urban areas.
The areas in Northern Kentucky, near Cincinnati, the Western Kentucky towns that border Illinois and Missouri and the southern areas near Nashville are heavily Republican. But the Democrats in these areas are not as liberal as in Louisville and Lexington, nor as affected by the coal industry as in Eastern Kentucky.
In Oregon, Can Sanders Run Up The Margin?
Sanders trails by about 300 pledged delegates (Clinton has 1,717, Sanders 1,437). Kentucky (61 delegates) and Oregon (74) are not very significant in that delegate race, with massive states like California (546) and New Jersey (142) to vote next month.
But in closing the delegate margin, it would helpful for Sanders to run up huge margins the way Clinton did in the South, getting more than 70 percent of the vote.
Oregon could be an ideal state for an overwhelming Sanders win. It has the kind of the rural areas where he has been strong and its urban core, unlike most cities, is not heavily-black.
Multnomah County, which includes most of Portland, is just 6 percent African-American.
This story first appeared on NBCNews.com.