WASHINGTON (Reuters) - A political newcomer who thrilled Democrats with a strong finish in a Georgia congressional race - despite attacks by President Donald Trump - will face an experienced Republican candidate in a June runoff election for a district long dominated by the party.

Democrat Jon Ossoff drew 48.1 percent of the vote in Tuesday’s special election, just shy of the 50 percent needed to win the most closely watched U.S. congressional race since Trump took office in January. Some saw the election, held to replace new Health Secretary Tom Price, as a test of the Republican president’s political strength.

Ossoff, 30, was the top vote getter in a field of 18 candidates, 11 of them Republicans, in a suburban Atlanta district that has sent Republicans to Congress since the 1970s. Republican Karen Handel, 55, a former Georgia secretary of state, won 19.8 percent, and will face Ossoff in the June 20 runoff.

The runoff presents a stiffer challenge. If Ossoff gets the support of the other Democratic candidates, he would have 49 percent, said Democratic National Committee Chairman Tom Perez.

However, Perez said the party would target up to 35,000 Democrats who voted in November’s presidential election but not on Tuesday.

“We have an army of volunteers,” he told CNN.

Handel, who said Trump called to congratulate her on Wednesday morning, dismissed Ossoff as a well-funded novice who would flounder as Republicans consolidated support behind a single candidate.

“We know that this is an important race, and it’s going to stay in the hands of a Republican,” Handel told CNN. “It is all Republicans, all hands on deck.”

Demographic changes have made Georgia’s affluent 6th Congressional District more competitive for Democrats.

Slideshow ( 14 images )

Trump won the district by only 1.5 percentage points in November against Democrat Hillary Clinton, who drew support from its many college graduates.

Republican U.S. Senator Lindsey Graham of South Carolina said the race showed how the South was changing. “This should be a wake-up call for the Republican Party in the South,” he told NBC’s “Today” show.

Slideshow ( 14 images )

Ossoff, a former congressional staffer and documentary filmmaker, ran on a pledge to “Make Trump Furious.”

Trump jumped into the race in its final days with attacks on Twitter poking fun at Ossoff for not living in his own district and for attracting support from Hollywood celebrities.

The president weighed in again on Wednesday with a tweet saying, “It is now Hollywood vs. Georgia on June 20th.”

In response, Ossoff portrayed Trump, a New York businessman who had never held public office, as the Washington insider.

“Folks in Washington tend to overstate their influence in local races like this,” he told MSNBC. “This comes down to grassroots intensity.”

White House spokesman Sean Spicer said Trump would campaign in Georgia for Handel “if needed” but dismissed the race as overhyped.

“The Democrats went all-in on this race,” Spicer told reporters. “They lost.”