en.wikipedia.org/wiki/Tacitus_(emperor)

Modern reference works do not support a consulship of Tacitus under Valerian.

• The De Imperatoribus Romanis entry on Tacitus says: “We have no reliable information on the earlier career of the Emperor Tacitus. All that is known with any degree of certainty is that in 273 he was consul…” It adds that “all the statements in the Historia Augusta regarding Tacitus' earlier career … have been rejected by historians as fictitious.” The same entry then states: “Tacitus held the consulship at least twice, first in 273 and again in 276.”
• The modern online Roman Imperial Coinage (RIC V.1/2) history likewise says Tacitus “was consul for the first time in 273 and, according to the Fasti, was consul for the second time in 276.”

So the article’s wording is incorrect in two ways:

1. it places one consulship under Valerian, which rests on the unreliable Historia Augusta tradition; and
2. it omits the securely attested second consulship in 276.

A corrected version would say that Tacitus is attested as consul in 273 and again in 276, while claims about a Valerianic consulship belong to later unreliable biography.

This sentence repeats the late antique senatorial-election narrative, but modern evidence points the other way.

• The De Imperatoribus Romanis entry states that the most reliable sources, Zosimus and Zonaras, say Tacitus “was chosen Emperor by the army” after Aurelian’s assassination, and that he then went to Rome “where he was confirmed as Emperor by the Senate.”
• The modern RIC V.1/2 historical synthesis is even more explicit. It says the literary sources developed the “myth of the ‘election’ of Tacitus by the Roman Senate” and that coinage shows Tacitus had already been proclaimed emperor before arriving in Rome. It concludes that the military imagery and dated issues from his adventus in Rome “disproves the theory that Tacitus was the old princeps senatus present at Rome when he was elected by his peers, or else a senator who had retired from affairs of state and who was brought back from his countryside retreat.”

So the problem is not just uncertainty: the article states as fact a scenario that modern numismatic and historiographical work specifically argues against. The Senate’s role was one of recognition/confirmation, not the original election of a retired senator in Rome.

This statement presents a dramatic restoration of senatorial constitutional power as fact, but modern scholarship does not accept that.

• The De Imperatoribus Romanis entry notes that the key passages behind this picture come from the Historia Augusta, and states that the “overwhelming consensus among historians” is that these passages are “unhistorical.” In particular, it says there is “no credible evidence” that Gallienus’s exclusion of senators from military affairs was even temporarily reversed under Tacitus.
• The RIC V.1/2 historical analysis says the literary tradition built a myth of Tacitus’s senatorial elevation and restoration. It adds that modern attempts to find evidence for a “senatorial restoration” rest on very limited evidence, and then dismantles the usual numismatic/epigraphic arguments one by one:
  • the inscription calling Tacitus verae libertatis auctor probably refers to military victory or tax privileges, not restored Senate power;
  • the supposed Libertas Aug coin used to support the theory “has never existed” and is a misreading of Ubertas Aug;
  • the Restitut Rei Publicae medallion is a standard military restitutio orbis type, not proof of Senate constitutional authority;
  • SC marks on gold coinage do not show a revived senatorial right to issue coinage.
• The same RIC synthesis concludes that Tacitus “was in no way a champion of the senatorial cause.”

In short, the article turns a highly doubtful literary construction into a concrete legal program. The surviving evidence does not support the claim that Tacitus restored to the Senate, by law, the right to appoint emperors, consuls, or provincial governors, nor the other sweeping powers listed here.