>>>To the best of knowlege the last major talmud chocom in goverment service was Rav Meir Shapiro and he was in the Semp, not CR
The Reise Rav (Rabbi Aharon Lewin) and Rav Alexander Zusia Friedman (author of the Meyaneh Shel Torah) Hashem Yinkom Domom were among the Agudah elected members of the Sejm after him
The Ponivitcher Rov was also a member of the Lithuanian parliament after that.
As far as chief rabbis go: Rabbi Yehuda Levin, chief rabbi of Moscow (died 1970) was also a major a Talmid Chochom, a close chaver of Rav Yaakov Kamenstsky from when they learned together in Slobadka.
Given his position he also did controversial things. His life and success as chief rabbi depended his acting like a Soviet Union propagandist and claiming that the Jews are NOT being persecuted there.
When he came to the US in 1968 secular Jewish groups hounded and heckled him . It was the lhavdil elef havdolas Gedoley Torah like Rav Moshe and Rav Yaakov who stood by him and apparently agreed with him that it is worth saying Soviet propaganda in exchange for maintaining some semblance of Jewish life in Russia such as shul activities and matzoh-baking etc.
When he spoke at secular venues there was open jeering at him because of the Soviet propaganda about the treatment of Jews there that he had to say . When he spoke at the Sefardsher shul in Boro Park Rav Yaakov Kamenstsky introduced him with the highest amount of respect talking about how we are about hear from the most chosuv alumni of Slabodka etc.(although he did hint that you have to understand that Rabbi Levin is speaking in code) The crowd which included many Talemdey Chachomim listened to him and accorded the highest respect .Even the streets around the shul were packed with police and police barricades to prevent the mob of people who wanted to meet him and hear from him.