Question: What was political office did Gaius Silius hold and was considered the highest elected political office of the Roman Republic?

Context articles: Li Chengpeng
Claude Lightfoot
Roman consul
List of Roman consuls designate
Gaius Silius (consul designatus 49 AD)
Lucius Apronius
Gaius Silius
James Bourque
Military tribune
List of undated Roman consuls

Li Chengpeng () (born September 22, 1968) is a prominent writer and social critic in the People's Republic of China.
 Well known in China for his reportage and social commentary—Li's Sina Weibo blog had nearly six million followers — (it is offline now) Li made international headlines in 2011 when he announced that he would seek political office as an independent candidate in his hometown of Chengdu, Sichuan province.
 While not technically illegal, the decision represented a rare and bold move in a country where candidates for political office are typically appointed by the Communist Party of China.
Claude M. Lightfoot (1910–1991) was an African-American activist, politician, and author.
 From 1957 until his death in 1991 Lightfoot was an officer of the Communist Party of the USA (CPUSA) and was several times the nominee of that party for elected political office.
 The author of many books and articles about racism and communism, Lightfoot also traveled and lectured throughout the world.
A consul was the highest elected political office of the Roman Republic, and the consulship was considered the highest level of the "cursus honorum" (an ascending sequence of public offices to which politicians aspired).
This is a list of Roman consuls designate, individuals who were either elected or nominated to the highest elected political office of the Roman Republic, or a high office of the Empire, but who for some reason did not enter office at the beginning of the year, either through death, disgrace, or due to changes in imperial administration.
Gaius Silius (c. AD 13 – 48) was a Roman senator who was nominated as consul designate for 49 AD, but was executed by the emperor Claudius for his affair with the empress Valeria Messalina.
Lucius Apronius was a Roman military commander active during the reign of Tiberius.
 Apronius shared in the achievements of Vibius Postumus and earned the ornaments of a triumph for his distinguished valor in Dalmatian revolt and Germanic Wars, along with Aulus Caecina Severus and Gaius Silius in 15 AD.
 In the Senate, Apronius in 22 procured a decree of votive offerings should be made, due to the successful prosecution of Gnaeus Calpurnius Piso, who had engaged in subversive plotting against Tiberius.
Gaius Silius (died AD 24) was a Roman senator who achieved successes as a general over German barbarians following the disaster of the Battle of the Teutoburg Forest.
 He had been appointed consul in AD 13.
 However, Silius became entangled in the aftermath of Sejanus' fall and was forced to commit suicide.
James W. Bourque, PC (December 17, 1935 – October 19, 1996) was a First Nations activist, who in 1992 became one of the few Canadians ever appointed to the Queen's Privy Council for Canada who had not previously served in an elected political office.
A military tribune (Latin "tribunus militum", "tribune of the soldiers", Greek "chiliarchos", χιλίαρχος) was an officer of the Roman army who ranked below the legate and above the centurion.
 Young men of Equestrian rank often served as military tribune as a stepping stone to the Senate.
 The "tribunus militum" should not be confused with the elected political office of tribune of the people "(tribunus plebis)" nor with that of "tribunus militum consulari potestate".
This is a list of Roman consuls, individuals who were either elected or nominated to the highest elected political office of the Roman Republic, or a high office of the Empire, but for whom an exact date of when they served in office is absent.
 Most are reckoned to be suffect consuls, but occasionally it encompasses an ordinary consul.