私は政治家になりたかったのだが。    I would like to become a politician.

願望表現の仮定法
I wish I were a bird               I hope that you will pass the exam. (直接法)
I wish you would(could) pass the exam.
                                                       would  could  might  should
時間的にひとつさかのぼらせると
I wish (taht) you had passed the exam.
                     仮定法・過去完了(裏切られた過去の事実)
I wish (taht) you |would| have passed the exam.
                       |could |

want  make  have  get ,   that節(名詞節)をあとに取れない動詞である
 x I want that.......  x I make that........  x I have that....... x I get that......
I  want  you  to pass  the exam.
S   V      O        C         O'