For those seeking definitive answers about American politics in the Trump era, the result in Georgia’s sixth congressional district was both illuminating yet somehow uniquely unsatisfying.

By winning just over 48% of the vote in a splintered field, Democrat Jon Ossoff far outpolled past Democratic candidates in the prosperous Atlanta suburbs that make up his district. However, in the “jungle primary” format in which he competed against 17 other candidates from both parties, that 48% was insufficient for Ossoff to win and forces a runoff in two months when he will face Republican Karen Handel.

The race had already drawn well over $15m in spending and that total is likely to triple in the coming months. Ossoff, who became a symbol of hope for national Democrats desperate for any electoral victory, raised over $8m, 95% of which came from outside the district. However, outside conservative groups poured money into anti-Ossoff ads designed to boost Republican turnout and keep the Democratic hopeful under 50%.

Although the district, formerly represented by the health and human services secretary, Tom Price, had been a traditionally Republican one – it was even represented by Newt Gingrich when he became speaker of the House in 1994 – it is in some ways unique. It is a prosperous area with a mean household income of $116,000 where nearly 60% of the residents have a college degree. It is also diverse, with rapidly growing Hispanic and Asian American communities.

Until the emergence of Donald Trump, it had been considered safe Republican territory. However, Hillary Clinton narrowly lost it at last year’s presidential election, despite winning in similar well-educated, traditionally Republican, suburban areas. The result was that Ossoff’s campaign became a test not just for Democratic enthusiasm in opposition to Trump but of the rapidly changing political map in the United States, as blue-collar rust belt whites increasingly vote Republican but college-educated voters in the sun belt start to embrace the Democratic party.

The runoff means that the final result on 20 June will come after an intervening special election in Montana, which has also drawn significant national attention. Although political dynamics in the contest for Montana’s at-large congressional seat are very different than those in suburban Atlanta, that race too has become a focus for national Democrats. Ossoff’s strong showing in Georgia is likely to boost energy and fundraising for Rob Quist, the Democratic candidate in the special election there. Just as a surprisingly strong showing for a Democrat in a bright red congressional district in Kansas in early April boosted interest in Ossoff, his performance will help in Montana.

But Ossoff’s result will also have an effect on dynamics on Capitol Hill. Some 23 Republicans hold districts that were won by Hillary Clinton; these are disproportionately prosperous, well-educated and suburban, just like Georgia’s sixth. Even if Ossoff does not pull off a victory in the June runoff, the mere fact that his performance roughly mirrored Clinton’s against Trump is a warning sign to those Republican members of the vulnerable position Trump has placed them in – particularly if Trump’s dismal favorability ratings do not significantly improve. For these members, it doesn’t particularly matter that Ossoff didn’t win. It does matter greatly that he not only matched Hillary Clinton in the district but exceeded her share of the vote by just over one percentage point.

In the short term, the Georgia runoff is likely to be long-drawn-out battle. Both candidates will be amply funded and both present unique vulnerabilities. The 30-year-old Ossoff will face continued scrutiny over the fact that he does not live in the district and about his relatively opaque stances on a number of issues that Republicans, including the president on Twitter, have used to attack him as liberal.

However, his opponent, Karen Handel, is a veteran Georgia politician who had previously lost two statewide primaries for governor and US senator before making it to the congressional runoff on Tuesday night with just under 20% of the vote. She has long been a lightning rod for controversy and came to national attention during her stint at the Susan G Komen for the Cure breast cancer charity when she forced the group to defund Planned Parenthood. Handel was forced to resign in the uproar that followed and the group quickly reversed its position.

The result is that in a divided, highly energized electorate each side will try to motivate its base. Democrats will tie Handel to Trump and try use the specter of Planned Parenthood to win over suburban women while Republicans will paint Ossoff as a leftwinger who will be a knee jerk supporter of Nancy Pelosi. It will be expensive, it will be ugly and it will be close.