Germany's rising nationalist party has offered a prize of 100 euros (112 dollars) to anyone who can find "verifiable evidence of voter irregularities" at Sunday's election in the former East German state of Mecklenburg-Vorpommern.
Citing concerns of vote fraud, the Alternative for Germany (AfD) - which has evolved from a eurosceptic party to a right-wing protest party against Chancellor Angela Merkel's open-door refugee policy - has repeatedly called on supporters to pay close attention at polling stations.
The Austrian presidential election and the state poll in Saxony-Anhalt earlier this year show "that flagrant vote count irregularities cannot be ruled out, even in democratic states," said Leif-Erik Holm, the AfD's top candidate in the mostly rural state.
Mainstream parties have criticized the AfD for insinuating that ordinary citizens may commit electoral fraud, thereby undermining faith in the democratic process.
The AfD is currently polling at 21 per cent in Mecklenburg-Vorpommern, meaning it is sure to clear the 5-per-cent threshold required to enter the state parliament for the first time.
Austria's Constitutional Court found that ballots and voting results were handled improperly in the country's May presidential election, prompting a rerun scheduled for October 2.
There were several isolated incidents of voter irregularities at the Saxony-Anhalt election, one of three state polls on March 13 that resulted in dramatic gains for the AfD.
The AfD's growing popularity has eaten into the vote share of Mecklenburg-Vorpommern's governing coalition, which is made up of the Social Democratic Party (SPD) and Merkel's Christian Democrats (CDU). They are currently polling at 28 and 22 per cent respectively.
Speaking at a campaign event in the city of Schwerin late Monday, Merkel vowed to "integrate" voters that the CDU has lost to the right-wing AfD into the political centre.
"We have to keep engaging with them, to show solutions and deeds. Voters can only be won back with solutions to problems," Merkel said.