What should you do? Make another job search or bite the bullet? If you find out almost immediately that you've made an error in accepting the job you did, there are several additional possibilities. You may want to reopen discussions with companies which made offers that you refused. In addition you may still have some momentum from your campaign and several possibilities may come up in your first few months on the new job. Your best bet, though, may be to meet the problem head-on. By this I mean you might approach your boss and lay the cards on the table, suggesting that you phase out of the company over a period of several months and switch from a salary to a consulting (for example, per diem) basis. This will provide a means of covering up this mistake in your future job search.
If neither of these solutions seems practical, and you decide to make a change, carefully plan when to do it. Ultimately only you can answer this question, but careful consideration can help minimize your emotional reaction and thus facilitate making a sound decision. What is an acceptable time frame with a loser job? This is a time to be really conservative. A period of a few months on a job can look very poor on your record. In addition, it will not be easy to put on a new job campaign since you have just been through one unsuccessfully. Your friends and contacts will help, but much less enthusiastically than they did before. Your finances are probably in poor shape at the moment. Therefore, recognizing that your career will probably span 40 years or more, spending a year or two on this job may be best in the long run. If you decide to do this, do it with a commitment to a maximum effort to develop yourself for the future as much as you can on the job. Coping with a bad job situation and learning how to make it better can be a valuable experience. No matter how good your next job is, you will run into periods when it doesn't seem to be going well. Being more effective in coping with this condition can be a help to you. Also ask yourself which of your goals are possibly achievable while you are with your current company, and which aren't. Then make a strong effort to reach the achievable goals. They may be useful in minimizing the effect of the black mark of a one- or two-year tenure on a poor job.
Conclusion
If your campaign has been successful, let's hope it's been constructive in terms of your long-term future. Your job campaign has forced you to examine your long-term goals in depth, and it should have resulted in a job in line with them. Many of your peers may seem fortunate in that they have not had to go through this process. On the other hand, they may find themselves "locked in" to jobs that they're not particularly happy with and that don't promise the futures they'd like. Also in your campaign you have sharpened some old skills and learned some new ones which may be useful the rest of your life. Above all other things, you should have learned that you can control your career to a much greater extent than you realized before. You also should have emerged from your campaign a different person - more realistic, better directed, and more effective. Undoubtedly it hasn't been an easy time. But a really good job for you at this stage of your career can provide you with one of the greatest satisfactions of your life.
Good luck and good hunting!