Voters in Georgia will cast their ballots Tuesday in the presidential primary as Democrat Hillary Clinton and Republican Donald Trump look to leverage their leads — and their rivals try to stop their marches to nomination.

Georgia offers the second-biggest delegate haul of the dozen states holding votes on Tuesday, trailing only Texas in clout on Super Tuesday. But it's arguably the most important state in the day's Republican contest, since Texas is also the home of Sen. Ted Cruz, who is favored to carry his native state.

Polls show that both Clinton and Trump have sizable advantages in Georgia. A WSB-TV poll released Monday has Clinton with a nearly 50-point lead over Vermont Sen. Bernie Sanders, who has shifted his resources on states in the Midwest and Northeast. In the same survey, Trump leads a crowded field with nearly 40 percent of the vote.

Georgia's "winner-takes-most" Republican delegate rules adds an extra layer of intrigue to the night's contest. Candidates can only get delegates if they reach 20 percent of the statewide vote or if they finish first or second in one of Georgia's 14 congressional districts.

The polls in Georgia are open from 7 a.m. to 7 p.m. Here's a few things to watch:

Bellwether counties: So go DeKalb and Dawson counties, so go Georgia. Dawson County in north Georgia has voted for the winning candidate in 55 of the 59 statewide GOP primaries held in Georgia since 1996, making it Georgia's top Republican indicator. And DeKalb voters have picked the winning candidate in 42 out of 44 statewide Democratic primaries since 1996. Watch those two closely tonight, and read more about their prognostic powers here.

The black vote: Clinton crushed Vermont Sen. Bernie Sanders in South Carolina with the help of an overwhelming majority of black voters, and she's hoping to repeat the same fete in Georgia, where black voters also make up the bulk of the Democratic electorate. Sanders has tried to make inroads with black voters with the help of surrogates like rapper Killer Mike and state Sen. Vincent Fort. He also trekked to Morehouse College two weeks ago in a bid to win over black students. If he can't connect with more undecided African-American voters, he's in for a long night.

North Georgia: The upper third of the state is also the seat of Georgia's Republican power base. Gov. Nathan Deal, Lt. Gov. Casey Cagle and House Speaker David Ralston all hail from the Peach State's upper reaches of the state, which is also home to some of the nation's most conservative congressional districts. The tea party sentiment that swept the nation six years ago took root there, and polls show a disgust with Washington remains strong. This is where Trump and Cruz will battle for anti-establishment votes. The remaining Democrats in the area, meanwhile, tend to be overwhelmingly liberal - meaning that Sanders will have to rack up big margins here to cut into Clinton's lead.

Moderate Republicans: Florida Sen. Marco Rubio and Ohio Gov. John Kasich will duke it out for the support of more moderate Georgia Republicans in the vote-rich Atlanta suburbs and in the low-lying coastal areas stretching from Savannah south to Brunswick. The WSB poll shows Rubio is on the cusp of the 20-percent mark he needs to secure a chunk of the 76 Georgia GOP delegates at stake, and he has visited Atlanta twice in the past three days to try to drum up more support. But Kasich has a fervent core of supporters, and he targeted more moderate Sandy Springs voters with a campaign stop last week.

Voter turnout: More than 400,000 Georgians have already cast ballots for the presidential election through in-person early voting, smashing the state's record set eight years ago. The brunt of those ballots, more than 240,000, were cast in the Republican race. Secretary of State Brian Kemp said the early numbers point to a strong turnout Tuesday, thanks partly to a recent surge of visits by presidential candidates. Higher turnout on the Republican side is likely to benefit Trump's campaign, although Rubio's advisers say they expect many late-breaking voters to side with their campaign. On the Democratic side, Sanders relies on first-time voters, so a surge of last-minute interest could help him blunt Clinton's advantage.

What's at stake

Georgia awards 102 delegates in the Democratic race (plus another 15 super delegates) and 76 in the GOP contest.

On the Republican side, 42 of the delegates are allotted by congressional district. Any candidate who wins a majority of the votes in a district gets three delegates, but if no one reaches that mark, then the winner gets two delegates and the runner-up gets one. Thirty-one are statewide GOP delegates, which operate under the same rules. All 31 go to a candidate who wins more than 50 percent of the vote, but if no one reaches that mark, they are divvied up between each candidate who wins more than 20 percent. The remaining three are Republican National Committee delegates bound by statewide votes.

The Democratic rules are a bit different. Each of Georgia's 14 congressional districts awards between 4-7 delegates proportionally among winners with at least 15 percent of the district vote. That accounts for 67 of the state's haul. Another 22 delegates are split proportionally among candidates who win at least 15 percent of the statewide vote. Thirteen more are leadership delegates also divvied up by statewide support. Not up for grabs are the 15 super delegates - party elites who can support anyone they wish. Most have already declared for Clinton.

Georgia is among a dozen states where voters will cast ballots on Super Tuesday. (Republicans in Wyoming and Colorado will also start caucusing on Tuesday but won't release results until later.) It's at the center of the SEC Primary, a band of southern states that includes Alabama, Arkansas, Oklahoma, Tennessee, Texas and Virginia. But a disparate cluster of other states also hold votes on Tuesday: Alaska (Republicans), Colorado (Democrats), Massachusetts, Minnesota and Vermont.

It's an epic day. There are 865 Democratic delegates up for grabs - roughly one-fifth of the total needed to lock down the nomination. Republicans will award 595 delegates - that's about one quarter of the haul needed to lock up the party's nod.