The office in the southwestern town of Trzebnica is used by Michał Jaros, a lawmaker and a deputy minister for development and technology. He also heads the ruling Civic Coalition (KO) in the Lower Silesia region.
The slogans "Down with Tusk" and "Hands off Republika" were painted on a window and the building's façade.
Daria Szydłowska, a spokeswoman for Trzebnica police, said officers had inspected the site, secured surveillance footage and questioned witnesses.
The vandalism came a day after investigators demanded that TV Republika hand over evidence in a separate inquiry into allegations that the broadcaster had encouraged viewers to share private information about a police officer who took part in an operation outside Poland's Constitutional Tribunal on October 16, state news agency PAP reported.
The officer's personal information was subsequently made public without her consent and in circumstances that could have put her or her family at risk, public broadcaster TVP Info said.
TV Republika staff have also been accused of making insulting and degrading remarks about police officers and the prime minister on air, as well as threatening officers amid a dispute over the constitutional court.
The row involves the government and right-wing opposition parties, which are at odds over the Warsaw court, along with media outlets aligned with the opposing sides.
On Thursday, another private right-wing broadcaster, wPolsce24, refused to hand over footage of an October 16 demonstration outside the court.
(gs)
Source: IAR/PAP, TVP Info