Editor’s Note: Julian Zelizer is a history and public affairs professor at Princeton University and co-host of the “Politics & Polls” podcast. In January, Norton will publish his new book with Kevin Kruse, “Fault Lines: A History of the United States Since 1974.” Follow him on Twitter: @julianzelizer. The opinions expressed in this commentary are those of the author. View more opinion articles on CNN.

(CNN) —  

As he tweeted Sunday morning, President Donald Trump will soon be on his way to rally voters in Mississippi. There he hopes to bolster the election prospects of Senator Cindy Hyde-Smith, the former Mississippi Commissioner of Agriculture and Commerce, who Governor Phil Bryant appointed in March to fill the Senate seat of the retiring Thad Cochran.

In the November 6 election, none of the candidates – Hyde-Smith, Democrat Mike Espy or Republican Chris McDaniel – received a majority of the vote. Hyde-Smith and Espy obtained enough of the vote to qualify for the runoff, while McDaniel did not.

When the runoff takes place this Tuesday, Mississippi voters will offer the nation evidence as to whether “moderate white voters” still exist in the Deep South. These voters may signal if Democrats or moderate Republicans can be viable future candidates in red states, and in rural areas in otherwise purple states.

Senator Hyde-Smith is an ultra-conservative politician. She is one of the Republicans who shows there is little daylight between Trump and the rest of the Republican Party anymore. According to FiveThirtyEight, she voted with the President 100% of the time – a figure that makes sense given her strong support of Trump’s hardline views on immigration, gun rights and anti-abortion policy.

But, since Election Day, a series of stories have suggested her strong sympathy with the forces of white nationalism. Seeking to be elected in a state that holds the invidious distinction of having the highest number of lynchings between 1882 and 1968, Hyde-Smith made a shocking comment that she would be in the “front row” of a “public hanging” if one of her supporters invited her (She later apologized if her comment had offended anyone).

CNN’s KFile has reported that during her time in the state legislature she pushed for a resolution honoring a 92-year-old woman for being the “last known living ‘Real Daughter’ of the Confederacy living in Mississippi,” whose father fought for Robert E. Lee. The resolution praised the father for fighting to “defend his homeland.”

And it only gets worse from there. Hyde-Smith, who attended one of the notorious white academies set up in the 1970s to avoid racial integration, joked at Mississippi State University about the need to suppress student votes. And a photograph surfaced of her proudly surrounded by Confederate artifacts – with a caption that read: “Mississippi history at its best!”

Hyde-Smith has enough stains on her record to make her unacceptable to large swaths of the electorate. In an era when much of the country has greatly advanced in terms of accepting the principles of racial pluralism, social equality and human rights, there should be no political space for a politician who makes a statement about public hangings on the sacred ground where African Americans were brutally slain by whites simply because of the color of their skin.

But the questions remains: Are the statements and historical record as damaging as the sexual assault and child molestation allegations that helped bring down Alabama’s Republican Roy Moore in his Senate campaign against Democrat Doug Jones?

The answer is not clear. Mississippi is a deeply red state, and Donald Trump carried it by double digits. In recent years, Democratic presidential candidates have performed poorly there and Republicans have won most state and local elections.

And yet despite this, polls show the runoff is unexpectedly competitive, with Hyde-Smith holding a small but significant advantage.

Espy, a moderate African-American who has devoted a good deal of his campaign trying to engage the state’s business community and white suburban voters who don’t like to see Mississippi’s image tarnished, is hoping to put together the same kind of coalition as Jones. His goal is to win over a combination of African Americans and moderate suburban whites. Experts believe that he’ll need approximately 20% of the white vote to win, along with high African-American turnout.

The outcome in Mississippi is particularly important since the midterm results in the Senate were much more mixed than in the House. Though Republicans maintained and even slightly expanded their control, Democrats made inroads in parts of the Southwest.

The results also said a great deal about the state of conservatism in staunchly Republican sections of the electorate. Whether or not they agree with all of the messages coming out of the White House, many voters were certainly willing to tolerate this kind of a Republican Party. In Florida, Georgia and Texas, Andrew Gillum, Stacey Abrams and Beto O’Rourke did worse in rural counties than President Barack Obama in 2012. Democrats also did badly in rural areas outside the South, such as in Ohio and Indiana.

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Trump’s ability to hold white Republican voters in those states will be crucial to his chances for re-election in 2020, where he will aim to recreate the same narrow Electoral College victory that hinged on the support of Republican voters while making small inroads into Democratic constituencies.

If Hyde-Smith pulls off a victory on Tuesday, it will suggest that in certain parts of the Republican map, Trumpian politics works just fine. Conservative candidates can veer far to the right of mainstream America on key social and cultural issues and still be victorious.

This would be a counterpoint to the electoral results in California and Texas, where Democrats made some serious inroads in traditionally Republican territory. It would mean that moderate white voters are not really a major presence in these parts of the country.

But if Espy is victorious, it would send reverberations throughout the political system. A victory for Espy would mean that there are certain lines that can’t be crossed and that voters are in play in the red parts of this country. Espy has the potential to demonstrate that Democrats can build coalitions with traditional base voters, such as African Americans, along with moderates who are sick and tired of the kind of values that Trump and Republicans leaders have openly embraced amidst some of the ugliest moments in our recent political history.