Jansa, from the conservative SDS, has been just ahead of incumbent Prime Minister Robert Golob's center-left coalition in opinion polls before Sunday's parliamentary elections.
The fight is hot. Golob has accused Jansa of bringing in the notorious Israeli security company Black Cube to use wiretapping to obtain compromising material. SDS has in turn pointed to EU Commissioner Marta Kos from Golob's alliance as a former police agent in the former Yugoslavia.
Well-known women's rights activist Nika Kovac is worried about Jansa's return.
"We will decide whether we want to live in a democracy or an authoritarian state," Kovac told the AFP news agency earlier in March.
