All eyes are on Montana as voters head to the polls Thursday to decide a pivotal House special election.

The race was already getting plenty of attention, but a physical altercation between GOP candidate Greg Gianforte and a reporter covering him has put it at the top of newscasts nationwide, worrying Republicans and giving more hope to Democrats for an upset.

The confrontation between Gianforte and Guardian reporter Ben Jacobs left both sides telling different stories. Jacobs and other witnesses said Gianforte lost his composure under questioning about the GOP healthcare bill, and that the reporter ended up on the ground with his glasses broken. Gianforte's side blamed Jacbos.

Police charged Gianforte with misdemeanor assault, which is hardly the headline he and Republicans wanted for the day of the election.

Before the episode, Republicans and Democrats already had been pouring money into the race between Gianforte and Democrat Rob Quist to replace Interior Secretary Ryan Zinke in the state’s sole House seat.

Both parties are watching the race closely for evidence of a mounting wave against President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE.

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Here are five things to watch .

Can Gianforte repeat Trump’s success in key counties?

Montana is a tricky state to predict. Pre-election polling is notoriously unreliable both because of the state’s size and the independent nature of its electorate.

Last year’s presidential election is proof of the state’s purple leanings. While Trump blew Democrat Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE out in the state by a 22-point margin, Gianforte lost his gubernatorial bid to Democrat Steve Bullock by 4 points.

Republicans are leaning on President Trump’s popularity in the state to win votes for Gianforte. Vice President Pence and Donald Trump Jr. both campaigned for him, while Trump and Pence appeared in robocalls days before the election.

As Thursday’s results come in, look to two big counties that voted for Trump but not Gianforte in 2016: Cascade and Lewis and Clark.

Trump outperformed Gianforte’s gubernatorial margin in Cascade by 33 percentage points and in Lewis and Clark by 30 points. Both are home to cities where Democrats need to perform well: Great Falls and Helena, respectively.

So if the electoral map looks more like the presidential one, Gianforte is in the clear. But if it starts to look like the one that lost him the governor’s race, he’ll obviously be in trouble.

One other tip, pointed out by ABC’s Ryan Struyk: Tiny Lake County in northwestern Montana has been an almost perfect bellwether county in Montana for two decades.

What will turnout look like?

Analysts always point to turnout as the key to every election. But with the vote scheduled for the Thursday before the Memorial Day holiday weekend, that warning is especially important.

Democrats and Republicans have fought for control of the narrative for months, keenly aware that an enthusiasm gap could spell doom. That’s one reason why Republicans have dumped so much money into the state, as they lag in 2018 generic ballot polls and are tied to a president with low approval ratings.

Since Montana is a massive state, many vote by absentee ballot. As of Tuesday evening, more than 250,000 voters returned their absentee ballots — more than a third of the 650,000 voters who were registered on Election Day 2016.

It could be difficult to use those numbers to predict the election’s outcome, but supporters of whoever wins will undoubtedly point to turnout as one reason for the victory.

Michael McDonald, an elections expert at the University of Florida, wrote Wednesday that Gianforte’s hopes could be boosted by the fact that the absentee ballot return rate in counties won by Clinton is below the statewide level.

But he added that Quist has good news in the absentee ballot figures, too — the number of absentee ballots returned in counties won by Clinton is up 16 percent.

Can Democratic populism win Trump voters?

Trump rolled through the Electoral College thanks in no small part to his populist appeal to white, working-class, rural voters who felt left out of the Obama economy.

Montana, a rural and politically independent state, could also serve as a battleground for two rival brands of populism.

Gianforte has leaned heavily on Trump and his surrogates to help connect with voters who delivered an emphatic win for Trump last year.

On the Democratic side, Quist, a popular folk singer in the state, is running as a populist Democrat — he joined with Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.) in a swing through the state last weekend.

Many Democrats have looked at the 2016 results as proof the party needs to connect more with the working class through economic appeals. But that requires a careful balance in red states, where voters could be turned off by liberal policies.

Quist’s race could help show whether the party has figured out how to walk that line in the states they will need to win back.

What’s the post-election spin?

Whichever candidate wins, control over a single House seat won’t have much effect over who controls Congress. But the real impact of Montana’s election could be its effect on the national narrative.

Democratic messaging and fundraising has been boosted by the fact that the reliably red district is even in play. But the GOP could blunt that momentum somewhat if they manage to hang on to the seat.

A Quist victory would prompt the party to declare that the anti-Trump “resistance” has taken its first congressional seat, warning that Trump’s scandals and low polling numbers suggest a 2018 midterm wave. That enthusiasm could be key as the party rolls toward the Georgia special election runoff on June 20, where a follow-up win would create significant momentum.

Republicans would be left shaking their heads, questioning if Trump is creating an electoral nightmare down the ballot and lamenting the millions blown on saving what was once a safe seat.

On the flip side, the spin of a Gianforte win would likely depend on the margin. A close race will send a mixed message: Democrats will still claim that the race would have been a blow-out without Trump, while Republicans push back, arguing that a win is a win.

A Quist loss will also likely prompt Democrats to question the party’s level of financial investment in the race. While the party organization has poured money into the Georgia special election, official committees have largely steered clear of Montana.

Some Democrats argue that the decision helped to keep Quist looking somewhat independent of the national party. But that strategy might lead to questions as it did earlier this year, when Democrats outperformed in Kansas only to still fall short with little national investment.

A comfortable Gianforte victory would be a major relief for Republicans. That result could dampen enthusiasm among Democrats and continue the demoralizing trend of liberals falling short of actually winning a special election seat, a trend that could jeopardize Democratic enthusiasm moving forward.

How will Trump respond?

With Democrats racing to frame the tightening in Montana as a referendum on Trump, it’ll be worth watching how the president takes the results.

Since he’s finishing up his first international trip as president, Trump will likely be awake when the race is called. He’ll be in Italy meeting with the Group of Seven countries, with a winner expected to be crowned around early morning in Trump’s time zone.

After Democrat Jon Ossoff failed to win April’s special election all-party primary in Georgia, forcing him into a runoff with Republican Karen Handel, Trump tweeted twice to mock the Democrats and claim some of the win for himself.

Shortly after midnight, as votes were being finalized, Trump chided the “major outside money” and “FAKE media support” that he said helped Ossoff.

“Glad to be of help!” he added

The next morning, he chided Ossoff for “failing” in another tweet.

The fact that Trump’s son and vice president campaigned for Gianforte in Montana raises the stakes for Trump’s electoral brand in the special election.

Read more from The Hill:

GOP on edge over Montana election