ROSWELL, Ga. — The most expensive House race in U.S. history heads to voters Tuesday in the northern suburbs of Atlanta.

Either Republican Karen Handel will claim a seat that’s been in her party’s hands since 1979 or Democrat Jon Ossoff will manage an upset that will rattle Washington ahead of the 2018 midterm elections.

Their matchup in Georgia’s 6th Congressional District has become a proxy for the national political atmosphere and a test of GOP strength early in Donald Trump’s presidency.

Here are things worth knowing about the race:

YOUTH VS. EXPERIENCE

Ossoff is a 30-year-old former congressional staffer turned documentary filmmaker. Making his first bid for office, he’s become a symbol of the Trump opposition movement.

Yet Ossoff barely mentions the president, talking instead in generalities about “restoring civility” and the importance of Congress as an oversight body. He doesn’t constantly refer to Handel, a former Georgia secretary of state, directly either, instead pitching his “fresh leadership” against “career politicians.”

Handel, 55, embraces her experience as a statewide and local elected official. “You know me,” she says, adding often that Ossoff has “no record” and “inflates his resume.”

She’s also known as a Susan G. Komen Foundation executive when the organization in 2012 sought to cut off its support of Planned Parenthood, which provides services including abortions.

IT’S A TRUMP DISTRICT

The Georgia 6th is an affluent and well-educated district that has elected Newt Gingrich, the former speaker; Johnny Isakson, now Georgia’s senior U.S. senator; and most recently Tom Price, who resigned in February to join the administration.

But even with that pedigree, Trump barely edged Democrat Hillary Clinton in November, giving Ossoff his opening once Price was confirmed. Ossoff hopes to maximize the district’s Democratic base and pick up just enough independents and moderate Republicans who don’t align with Trump.

Handel has handled Trump gingerly. She barely mentioned him ahead of finishing second to Ossoff in an April primary. She welcomed him for a fundraiser in late April, but it was closed.

Even a Trump Cabinet member and former Georgia governor, Agriculture Secretary Sonny Perdue, acknowledged the conundrum at a recent Handel rally, saying “some Republicans” are “turned off” by the president.

BIG MONEY

Ossoff raised more than $23 million, most from outside Georgia. He emphasizes it’s mostly from individual donors. Handel notes that many of those people live in Democratic-leaning states like California, New York and Massachusetts.

Of course, Handel’s benefited from outside money, too; it just hasn’t flowed through her campaign, which has raised less than a quarter of Ossoff’s haul.

The Congressional Leadership Fund, a political action committee backed by House Speaker Paul Ryan, has spent $7 million on her behalf. National Republicans’ House campaign arm added $4.5 million, and the U.S. Chamber of Commerce chipped in another seven figures. A chunk of the $5 million Handel raised herself came in three fundraisers headlined by Trump, Vice President Mike Pence and House Speaker Paul Ryan.