With campaign spending expected to top $50 million, the race to fill the suburban Atlanta congressional district, vacated when Tom Price was named Health and Human Services Secretary, is the most expensive in U.S. history. Both candidates in the 6th District are calling on heavy hitters with Georgia roots to get out the vote on Tuesday.

“It’s time to be knocking on those doors. It’s time to be making those calls. It’s time to be sending those emails,” Secretary Price told supporters at a weekend rally for Republican Karen Handel. “It’s time to be making certain that you are asking every single individual that you see within the 6th District, ‘Have you voted?’”

Former Georgia Gov. Sonny Perdue, a Republican, also stumped for Handel over the weekend, while Democrat Jon Ossoff enlisted the support of Rep. John Lewis, a Georgia congressman and civil rights icon.

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“With this election, it would indicate that people are prepared to change,” Lewis said at a weekend campaign event. “I think that many people will see the handwriting on the wall.”

The Real Clear Politics Average of polls shows Ossoff with a slight lead of 49.6 percent to Handel’s 47 percent in a district that normally favors establishment Republicans.

“This is exactly the type of district (Democrats) hope they can win if they can retake the House in 2018,” said Greg Bluestein, a political reporter with the Atlanta Journal-Constitution. “There’s 24 seats they need to win. A lot of them are going to be these fast-changing suburban districts that Republicans have long held.”

The GOP has held Georgia’s 6th District for nearly four decades. Ossoff hopes to fulfill a campaign slogan to “flip the 6th” from red to blue by appealing to moderate Republicans and independents.

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“I think this is an opportunity for Georgia to elect some fresh leadership that’s focused on delivering results for folks at home, focus on holding people accountable in Washington,” Ossoff told reporters while campaigning over the weekend.

In a district that Secretary Price won with 62 percent of the vote, but that President Trump won by less than 2 percentage points in November, Handel is rallying the conservative base by linking her opponent to left-wing Democrats.

Trump showed support for the candidate Tuesday morning in a tweet.

"KAREN HANDEL FOR CONGRESS. She will fight for lower taxes, great healthcare strong security-a hard worker who will never give up! VOTE TODAY," Trump tweeted at 6:02 a.m.

In another tweet, Trump blasted Ossoff, claiming he would raise taxes "to the highest level" and would be "weak on crime and security."

At a weekend rally, Handel won loud cheers when she told the crowd: “We are gonna rock Nancy Pelosi’s world.”

Both campaigns have beefed up security after receiving threats, including letters with a white powder mailed to Handel and some of her neighbors.

Although voter turnout is typically low in special runoffs, that has not been the case in Georgia’s 6th District.

Voters have already cast 140,308 early ballots, according to Georgia Secretary of State Brian Kemp. That’s more than double the 56,830 early ballots cast in the April 18 special election.

Fox News’ David Lewkowict and Emily Wakeman contributed to this report.