Jim Hacker first appears in Yes Minister having been recently re-elected as Member of Parliament for his constituency, Birmingham East, soundly defeating his opponents. His early character is that of a very gung-ho, albeit naive politician, ready to bring sweeping change into his department, unaware that Sir Humphrey and the civil service are out to stop any semblance of change, despite their insistence that they are his allies. Hacker is also noted as having challenged Humphrey while he was a member of the Opposition by asking difficult questions of his Permanent Secretary while testifying at a committee: Sir Humphrey stated that Hacker had asked "...all the questions I hoped nobody would ask," showing his new Minister to be at least a reasonably capable politician.
Before long, Hacker begins to notice that the Civil Service has been preventing any of his changes from actually being put into practice. Bernard is sympathetic to Hacker's plight and tries to enlighten his Minister as to the tricks and techniques employed by government staff, but his ability to help is limited by his own loyalties in the Civil Service. Hacker soon learns and becomes more sly and cynical - reminding us that he is, after all, a politician - using some of these ploys himself. While Sir Humphrey nearly always gets the upper hand, Hacker now and again plays a trump card, and on even fewer occasions, the two of them work towards a common goal.
Hacker also learns that his efforts to change the government or Britain are all really for naught, as he discovers in the episode "The Whisky Priest", when he attempts to stop the export of British-made munitions to Italian terrorists.
Throughout Yes Minister, there are many occasions when Hacker is portrayed as a publicity-mad bungler, incapable of making a firm decision, and prone to blunders that embarrass him or his party, eliciting bad press and stern lectures from the party apparatus, particularly the Chief Whip. He is continually concerned with what the newspapers of the day will have to say about him, and is always hoping to receive promotion by the Prime Minister (Hacker ran the unsuccessful campaign for a political ally during the Party's last leadership election - his man lost, becoming Foreign Secretary, and leaving Hacker nervous about his prospects under the winner, now Prime Minister). He is equally afraid of either staying at his current level of Cabinet seniority, or being demoted.
Just prior to the start of Yes, Prime Minister, Hacker shows a zeal for making speeches and presents himself as a viable party leader, after the Prime Minister announces his resignation, in the episode "Party Games". He is given embarrassing information about the two front-runner candidates, and manages to persuade them (by insinuating that secret information pertaining to both may be revealed to the public) to drop out of the race, and lend their support to him. With help from the recently promoted Sir Humphrey and other senior civil servants, Hacker emerges as a compromise candidate and becomes head of his party unopposed - and Prime Minister.
In Yes, Prime Minister Hacker strives to perfect all the skills needed by a statesman, giving more grandiose speeches, dreaming up "courageous" political programmes, and honing his diplomatic craft, nearly all of these attempts landing him in trouble at some point.
In a Radio Times interview to promote the latter series, Paul Eddington stated, "He's beginning to find his feet as a man of power, and he's begun to confound those who thought they'd be able to manipulate him out of hand."
Hacker becomes a more competent politician by the end. Though primarily interested in his personal career survival and advancement, he, unlike Sir Humphrey, views Government as a means rather than an end in itself.
Hacker has many prominent habits that feature throughout the series:
Drinking. Hacker enjoys various alcoholic beverages, particularly harder liquors, including scotch whisky: "the odd drinkie", as he likes to call them. He is seen drunk on more than one occasion, and even was caught drinking and driving in the episode "Party Games". He used his political immunity to escape charges.
Disdain for certain types of culture. Sir Humphrey thinks Hacker to be a cultural philistine who is unaware of the importance of protecting Britain's artistic heritage. Hacker believes it only important to the upper-class snobs (such as Sir Humphrey himself), and several other "wet, long-haired, scruffy art lovers", arguing that operas created by Italians and Germans are not representative of Britain's cultural heritage. However, upon becoming Minister for the Arts (in "The Middle-Class Rip-Off"), Hacker asks Humphrey if he could tag along on a gala night at the Royal Opera House. Humphrey is delighted by the volte-face and declares, "Yes, Minister!" enthusiastically. It should also be noted Hacker and his wife enjoy seeing foreign films, and in the same episode Hacker demonstrates some grasp of art, enough to make a strong case that a disputed art gallery in his constituency is not worth saving. (See also "Football" below.)
Pomposity. Hacker is often seen going off into sentimental, overly pretentious speeches either to himself or to Bernard and Sir Humphrey, holding his lapel on his suit jacket in a very royal manner. He also mimicked Napoleon by slipping his hand in the front of his suit jacket upon hearing he was selected by the party to become party leader and hence Prime Minister. However, it appears that Hacker's political idol is Winston Churchill: he occasionally speaks in the statesman's gruff style and is seen reading biographies of him.
Football. Hacker believes that sport is of a greater cultural importance and is even willing to sacrifice a local art gallery in order to bail out his constituency's football team, the fictional Aston Wanderers, that was being threatened with bankruptcy. He didn't support the team though, and was mentioned as being an Aston Villa supporter in the first episode.