Donald Trump intensified his efforts Tuesday to block Jon Ossoff from winning Georgia's special election with a Twitter barrage ripping the Democrat and a robo-call warning that he's a "liberal" puppet controlled by out-of-state interests.

"Don't let them do it," Trump said on the robo-call, which also claimed Ossoff would "raise your taxes, destroy your healthcare, and flood our country with illegal immigrants."

It's another in a series of increasingly visible steps by Trump to avoid an embarrassing defeat Tuesday that would be seen as a rebuke to his young presidency. The president sent five tweets between Sunday and Tuesday on the race.

They claimed the media is overplaying Tuesday's vote, said a vote for a Republican in the race is a vote for "lower taxes & safety" and referred to Ossoff as a "super Liberal Democrat."

He also sent two more tweets on early Tuesday, minutes before the polls opened, ripping Ossoff as "disaster" and predicting an "easy win" for Republicans in a runoff against him. He sent a sixth tweet later Tuesday, hours before the polls closed.

The robo-call, which was first reported by The Hill, and the three other tweets don't mention Ossoff by name, although it's clear he's referring to the 30-year-old former congressional aide. Ossoff's vows to "stand up to Donald Trump" have helped fuel his campaign, though at appearances he largely sticks to more moderate rhetoric that includes promises to cut wasteful spending.

Ossoff raised an unprecedented $8.3 million haul and has flooded the district with advertisements and volunteers. He's leading the polls in the 18-candidate field - all the contenders will share the same ballot regardless of party - but they show him short of the majority-vote he needs to avoid a June 20 runoff.

Republicans have held Georgia's 6th District, which spans from east Cobb to north DeKalb, for decades and Rep. Tom Price won landslide victories every two years until he was tapped as Trump's health secretary. But the president struggled in the district, winning it by less than 2 points, and Democrats hope Ossoff can deal Trump's presidency a stinging electoral defeat.

Ossoff's campaign had no immediate comment on the robo-call, but in an interview earlier Monday he called Trump's tweet "misinformed." In a statement, he said he was "focused on bringing fresh leadership, accountability, and bipartisan problem solving to Washington to cut wasteful spending and grow metro Atlanta's economy into the Silicon Valley of the South."

The Democrat has called for an "aggressive simplification" of the tax code and an immigration package that provides a path to legal status for those in the country illegally without felony records. He opposes plans to repeal the Affordable Care Act, but said he will work with Republicans to nix the medical device tax, offer small business tax credits and increase competition in the insurance market across state lines.

The White House is said to be closely monitoring the wild race, though the two tweets he sent on Sunday and Monday are the first time the president has publicly weighed in on it. He may have a chance to do so again: He is set to headline a National Rifle Association rally on April 28 in Atlanta.

More recent AJC coverage of the Sixth District: