In the first round of the Czech presidential election earlier this month, Jiri Drahos was variously portrayed -- without substantiation -- as a pedophile, a thief, and a communist collaborator.

The smears were part of a string of unfounded allegations in social media and on websites suspected of dealing in fake news.

Now that the pro-Europe challenger’s campaign in a second-round runoff against incumbent Milos Zeman, one of Russian President Vladimir Putin’s strongest allies in central Europe, is in full swing, the disinformation gloves have come off once again.

Within days of the start of the runoff, which will culminate in balloting on January 26-27, pro-Zeman websites and social media were sending out messages and publishing ads accusing the 68-year-old scientist of seeking to open the country’s borders to immigrants, playing on local fears of a possible influx of Muslim extremists.

“The deciding factor [in the second round] is expected to be the intensive disinformation campaign directed against Professor Drahos,” says Jakub Janda, deputy director of the European Values think tank in Prague.

“We’ve already seen a growing number of attacks related to migration and his personal affairs, which is likely to intensify,” Janda adds.

Much of the focus has been on about 30 or so pro-Russian websites that have published a raft of conspiracy theories, slanderous articles, and anti-Western rhetoric against the United States as well as NATO and the European Union, both of which count the Czech Republic among their members.

Meanwhile, the sites consistently praise Zeman, who opposes immigration and is seen as pro-Russian.

Zeman won the first round on January 12-13 with 38.6 percent of the vote, compared to Drahos’s 26.6 percent second-place showing.

"I was expecting this type of lies and disinformation, common slander," Drahos said in response to a wave of ads on January 18 that called him a “welcomer” in reference to wanting to increase immigration.

Drahos has repeatedly said during the campaign that he opposes quotas set by the European Union that would force member states to share asylum seekers, though he would accept a limited number if they met certain criteria.

Zeman, 73, has courted controversy since being elected four years ago by voicing antimigrant views, denigrating Muslims, and warming up to Putin at a time when Russia is unilaterally redrawing European borders and many in the West accuse Moscow of meddling in Western elections.

He once called the 2015 migrant crisis "an organized invasion" of Europe and has said that Muslims are "impossible to integrate."

During the campaign before the first round of voting, attacks against Drahos from sites such as aeronet.cz questioned his character, accusing him of collaborating with the StB, the communist-era secret police, even though he had been given a clean lustration by Czech authorities affirming that he never worked with the police.

For his part Drahos, a political novice who has railed against Zeman’s “unacceptable stance” toward Moscow, says he long expected more of the same before voters head back to the ballot box because “Russia is interested in our elections.”

"My adversaries are hoping that if they ram down people's throats [the false accusations] that I was an StB collaborator or a pedophile, it will stick with some voters,” Drahos says.

“I know Milos Zeman is coming with blows below the belt,” the soft-spoken chemistry professor adds.

Analysts have been warning for the past year about meddling, mainly Russian-backed, in the Czech election after suspected similar campaigns in votes in the United States, the Netherlands, France, and Germany.

Moscow has long sought to hold sway in the Central European country and intensified its Czech efforts after the outbreak of violence in eastern Ukraine by pro-Russian separatists sparked a backlash, according to the Czech Security Information Service.

Zeman’s pro-Kremlin comments and ties between Moscow and some of his senior aides have raised fears even further that Russia is making inroads with its influence.

Martin Nejedly, the president’s chief economic adviser, worked in Moscow and subsequently headed a subsidiary of Russian oil firm LUKoil until 2015, when it collapsed. The bankruptcy left the Czech state with a liability of more than $1 million, which LUKoil reportedly covered after Zeman warned that it could cost Nejedly his job at Prague castle.

Neither Nejedly nor another senior Zeman aide, Vratislav Mynar, has received full security clearance from Czech officials, reportedly in part over possible ties to Russia.

In response to disinformation fears, the Czechs set up the Center Against Terrorism and Hybrid Threats (CTHT) last year. A unit inside the Interior Ministry, its agents look to combat terrorism and radicalization.

Several websites dedicated to rooting out fake news, such as popravde.cz, manipulatori.cz, and the VolbyDezinformace Facebook page, have also been set up to knock down erroneous reports.

But Josef Slerka, head of the Independent Journalism Foundation in Prague, warns that by the time fake news has been refuted, it may be too late.

"The biggest danger of fake news is the so-called 'sleeper effect.' From the beginning, we know it was from an untrustworthy source, but in a few weeks we will forget it and we will just say next time that we've heard it somewhere," he said.

The attacks haven’t always flowed one way.

Zeman, who has the backing of the unreformed Communists and the far-right anti-EU and anti-NATO SPD party, has complained about allegations he is in ill health and will be unable to fulfill another four-year term.

The claims have been strongly rejected by the presidential office and Zeman's own physician.

There have also been reports that some social media websites were spreading a hoax to Zeman's voters that they did not have to vote since the incumbent president automatically advanced to the second round.

Some analysts are also skeptical about how much influence Moscow can really have on Czech voters.

Mark Galeotti, senior researcher at the Institute of International Relations in Prague, says that while he believes the Kremlin clearly has a “favored candidate,” Zeman doesn’t need help mobilizing his base.

“Zeman is able to do that himself quite well,” according to Galeotti.

“At other times it [Russian disinformation] is quite good for mystifying, creating that situation where you have no idea what the truth is. But again, this is a situation where most people have had a chance to make up their mind about Zeman,” Galeotti told the Financial Times.

Correction: This story has been amended to fix the date of the runoff to January 26-27.