If the state gives her a victory anywhere close to the 41-point landslide she got out of neighboring West Virginia last week, Team Clinton will have considerably more evidence to buttress its argument about her electability.
It would embolden her to assert she could win Kentucky in the general election against presumptive Republican nominee John McCain, and to claim that Democratic frontrunner Barack Obama is unable to expand the Democratic electoral map into states like Kentucky.
If Clinton wins by a larger margin than the one by which Obama is expected to beat her in Tuesday's other primary in Oregon, it would also amplify her assertion that she's ahead in total votes, if Florida and Michigan are counted.
A Kentucky landslide would serve another purpose: it would bolster her case that Obama can't win over the blue collar and elderly white voters who fill the state's voters rolls and who, the Clinton campaign argues, are necessary to beat McCain in November.
With that calculus in mind, here is what Kentucky political strategists and experts will watch for Tuesday:
How goes Montgomery County? In 1988 and 2000 - the last elections with no incumbent president on the ballot - this county of less than 25,000 residents in the Outer Bluegrass region of the state was within 5 percentage points of the actual statewide primary results.
That could be a good omen for Clinton, who held a commanding 28-point lead over Obama in the county in a Suffolk University poll taken May 17 - 18.
Statewide, the Suffolk survey put Clinton 26 points ahead of Obama--51 percent to 25 percent, with 11 percent undecided, 6 percent for John Edwards, 5 percent uncommitted (an actual option on Kentucky ballots) and the rest declining to respond.
The power of John Edwards. Kentucky could provide a good litmus test for whether the former North Carolina senator's endorsement will help Obama make inroads with the blue collar and elderly white voters who have flocked to Clinton.
Edwards, who dropped his own bid for the nomination in January, remains on the ballot in Kentucky and 6 percent of Kentucky Democrats intend to vote for him, according to the Suffolk poll, conducted in the days after Edwards endorsed Obama.
In West Virginia, another state dominated by blue collar white voters where Edwards was still on the ballot, he drew 7 percent of the vote. Clinton finished with a whopping 67 percent, leaving Obama with 26 percent.
Clinton herself told reporters last week in Rapid City, S.D.: "I imagine that Sen. Edward's endorsement will be of some help to Sen. Obama in Kentucky."
But David Paleologos, who directed the Suffolk poll, said Edwards' Kentucky supporters are unlikely to vote for Obama.
"These are people who, for whatever reason, have a high disdain for both candidates," he said.
Only 11 percent of respondents who picked Edwards had a favorable impression of Obama--compared to 56 percent who viewed him unfavorably.
Clinton didn't fare much better with Edwards' backers--17 percent viewed her favorably compared to 67 unfavorable.
The role of race. Exit polls in neighboring West Virginia found one in five voters admitted race was a factor in their vote. Of those, more than four in five voted for Clinton.
Kentucky, which is 91 percent white, has a larger black population than West Virginia.
And though Kentucky voters may also factor race into their votes, they also might be more reluctant to admit it to exit pollsters, said Laurie Rhodebeck, an associate political science professor at the University of Louisville.
"Voters get a little prickly here if you say race" drove their choice, she said. "They'll say, 'It's more that we're concerned about his church ties or his lack of military experience or that he seems so oung and untested.' Those may be socially acceptable ways of saying they're uncomfortable with a black candidate."
Obama's popularity numbers in Kentucky are similar to those he had in West Virginia before its primary, according to Suffolk polls taken in those states on the weekends before their primaries.
In Kentucky, 43 percent of the poll's respondents said they viewed Obama favorably versus 43 percent who had unfavorable impressions. In West Virginia, Obama had 44-percent favorability and 41-percent unfavorability ratings.
The battle for Louisville. Both candidates have strongholds in the state's biggest city, which is home to more than 700,000 of the state's 4 million residents, so turnout will be key.
Obama stands to do well in precincts in the city's West End, which has high concentrations of black voters, and in the Highlands, which is home to many University of Louisville academics and other educated professionals (as well as Clinton's state headquarters).
He has run lots of radio ads in the city and also has the support of its congressman, John Yarmuth (D-Ky.). At a state party dinner this month, Yarmuth boasted Obama intended "to contest Kentucky today … (and) believes Kentucky can be a blue state in November."
Clinton figures to do well in Louisville's South End, home to Ford and General Electric manufacturing plants and many of the white employees who work at the plants.
There is some speculation she could get a boost from G.E.'s acknowledgment last week that it may sell its appliance business, which is based in Louisville and employees 5,000 people there.
"That's precisely the type of issue that she's been addressing," Rhodebeck said. "So if voters were wavering about whether to vote or who to vote for, that bad news could be to Hillary's benefit."
In the rest of the state, Clinton is well-positioned in the nearly 50 counties in the eastern part of the state that are part of Appalachia, as well as in western Kentucky.
In order for Obama to hold down her winning margin, he needs to do well in Louisville and Lexington, home to the University of Kentucky, and in the relatively affluent northern Kentucky suburbs of Cincinnati.
Mind the (time-zone) gap. Kentucky polls are open from 6 a.m. to 6 p.m. But because the state is divided between the eastern and central time zones, polls in the eastern part of the state close one hour before those in the west.
Since the eastern part of the state is home to the areas in which Obama hopes to be competitive (Louisville, Lexington, the Cincinnati suburbs) and since cities tend to report more quickly than rural areas, early results may make it appear a closer race than it is.
The western part of the state, though less densely populated, is mostly Clinton country. Democratic turnout could be driven up in part of western Kentucky by the party primary for the congressional seat being vacated by Rep. Ron Lewis (R-Ky.).
As the western part of the state reports its results tonight, expect to see Clinton's margin widen.