4. Cn.DomitiusCalvinus, M. F. M. N., appears, in B. C. 62, as legate of L. Valerius Flaccus in Asia, and in B. C. 59 as tribune of the people, in which capacity he supported the consul M. Bibulus against the other consul, C. Julius Caesar, and the tribune Vatinius, who allowed himself to be used by Caesar as a tool. Three years later, Calvinus was praetor, and presided at the trials of L. Calpurnius Bestia, who was accused of ambitus, and of M. Caelius, who was charged with having attempted to poison Clodia. In B. C. 54 he offered himself as a candidate for the consulship, on which occasion he, as well as his competitors, was guilty of enormous bribery; and, in conjunction with C. Memmius, he entered into a most disgraceful compact with the consuls of the year, who were to preside at the elections. The two candidates promised to procure for the consuls in office certain lucrative provinces by perjury, if they would lend them their assistance in the elections; and in case the plan with the provinces should fail, the candidates promised to give to the consuls a compensation in money of forty millions of sesterces. C. Memmius himself afterwards denounced the whole plan to the senate; but the appointment of a court to investigate the conduct of Calvinus was prevented by intrigues. The election of the consuls also was delayed on account of unfavourable auspices. In the beginning of October, however, all the candidates were to be tried for ambitus; but they escaped judgment by the interreign which the party of Pompey tried to use as a means for getting him appointed dictator. The interreign lasted for nearly nine months, and Calvinus, who had in the meantime gained the favour of Pompey by voting for the acquittal of A. Gabinius, was at length made consul through the influence of Pompey. His colleague was M. Valerius Messalla. During the year of their consulship the disturbances at Rome continued : the candidates for the consulship for the year following, Milo, Hypsaeus, aand Metellus Scipio, as well as P. Clodius, who sued for the praetorship, carried on their contests with bribes, and had recourse even to force and violence. The consuls were unable to get their successors elected; a decree of the senate which they effected, that no one should obtain a foreign province till five years after he had held the consulship or praetorship, did not produce the desired results. During an attempt of the consuls to get their successors elected in an assembly of the people, stones were thrown at the consuls, and Calvinus was wounded.

For some years we now lose sight of Calvinus; but after the outbreak of the civil war in B. C. 49, we find him actively engaged in the service of Caesar's party, and commanding the cavalry under Curio in Africa. After the unfortunate battle on the Bagradas, he advised Curio to take to flight, and promised not to forsake him. In the year following, Caesar sent Calvinus with two legions from Illyricum to Macedonia, where he met Metellus Scipio, without however any decisive engagement taking place between them. But, according to Dio Cassius (41.51), he was driven by Faustus from Macedonia, and penetrated into Thessaly, where he gained a victory over Metellus Scipio, and took several towns. When Caesar broke up from Dyrrhachium to unite his forces with those of Calvinuis, the latter was in the north of Macedonia, and had nearly fallen into the hands of Pompey, but succeeded in effecting his union with Caesar on the frontier of Thessaly. In the battle of Pharsalia Calvinus commanded the centre, and was faced by Metellus Scipio.

After the close of the war in Thessaly, when Caesar went to Egypt, he entrusted to Calvinus the administration of the province of Asia and the neighbouring countries. While Caesar was engaged in the Alexandrine war, for which Calvinus sent him two legions from Asia, the latter became involved in a war with Pharnaces, the son of Mithridates; he was defeated in the neighbourhood of Nicopolis, and escaped with only a few remnants of his small army. After his return from Egypt, Caesar defeated Pharnaces near Zela, and Calvinus was sent to pursue the enemy, who was compelled to surrender Sinope. But soon after, a peace was concluded with him. As Caesar wanted to hasten to Italy, he left Calvinus behind to complete the settlement of the affairs in Asia. This does not appear to have occupied much time, for in the year following, B. C. 46, we find him engaged in Africa in besieging Considius at Thisdra, and in B. C. 45, he was present at Rome at the time when Cicero defended king Deiotarus. Caesar appointed Calvinus his magister equitum for the year following, but the murder of the dictator prevented his entering upon the office.

During the war of Octavianus and Antony against the republicans, Calvinus was ordered by the former to bring over reinforcements from Brundusium to Illyricum; but while crossing the Ionian sea, he was attacked by L. Statius Murcus and Cn. Domitius Ahenobarbus. His ships were destroyed, and he himself succeeded with great difficulty in escaping back to Brundusium. In B. C. 40 he was elected consul a second time; but before the end of the year, he and his colleague were obliged to resign, in order to make room for others. In the year following, he fought as proconsul against the revolted Ceretani in Spain. Here he acted with the greatest rigour towards his own soldiers, and afterwards defeated the enemy without difficulty. His occupations in Spain, however, appear to have lasted for several years, for the triumph which he celebrated for his exploits in Spain is assigned in the triumphal Fasti to the year B. C. 36. The sums of money which he had raised in the towns of Spain were spent partly on the celebration of his triumph, and partly upon the restoration of the regia on the via sacra, which had been burnt down. (Orelli, Onom. Tull. ii. p. 226; D. C. 38.6, 40.45, 46, 56, 42.46, 49, 47.47, 48.15, 32, 42; Plut. Pomp. 54, Caes. 44, 50, Brut. 47; Appian, App. BC 2.76, 91, 4.115, 116, Mithrid. 120; Caes. Civ. 2.42, 3.36, &100.78, &c., 89, Bell. Alex. 34, &c., 86, 93; Liv. Epit. 112; Vell. 2.78; Suet. Jul. 35, &c.; Fast. Cap.; Eckhel, v. p. 183.)