The Emperor’s control over a man’s senatorial career did not consist merely in starting men of obscure origin on their way by adlecting them into the Senatorial Order; it could be exercised at every step of the way both for those who were senatorials by birth and for those who were such by adlection.
This mixture was to be effected either by drawing the juries partly from the senate (of about 300 members), partly from an album of 300 equites (Plut. CG 5.2, Comp. 2.1), or by adlecting 600 equites into the senate and drawing the juries from this new senatorial order (Liv. Per. 60).
Trajan’s veto was not maintained, for Dig. 50. 2. 11 quotes a rescript of Severus and Caracalla approving the ancient custom at Nicomedia of adlecting decurions below the then prescribed age of 25.
1967, Richard Mansfield Haywood, Ancient Rome (McKay), page 473
The censorial power allowed him to exert an influence on the composition of the Senate, especially by adlecting men of mature years who had not been through the normal preliminary career but whose unusual ability came to his attention.