R. Yehudah Levi on religious political parties in Israel, from his Facing Current Challenges: Essays on Judaism (pp. 364-366):
[N]ot only is party activity not very helpful, it is actually detrimental precisely in the area in which it is needed most urgently--public relations and education. By their very nature and through no bad intentions, the religious parties may cause a chilul HaShem in a number of ways...
1. We mentioned earlier that presenting Torah in the framework of a party is in itself doubly problematic, indeed a double chilul HaShem. It symbolizes acceptance, on the part of Torah, of the sovereignty of the state; and it causes a disgrace to the Torah by presenting it as the concern of a small faction...
2. The smallness of the religious parties in the Knesset gives a false picture of the size of the Torah-observant community in Israel, as people tend to forget that many Torah Jews vote for other parties...
3. Whatever a politician says is obviously geared toward enhancing his party's prestige. This is readily understandable; that is hsi job. But this sensible approach robs the pronouncements of the religious politician of nearly all moral and religious value...
4. The realities of politics demand constant compromises... [W]hen the "representative of Torah" compromises on personal integrity and matters of interpersonal relationships, regarding which there are Torah guidelines, it is a humiliation and a disgrace of the Torah...
5. ...The activities of the present religious parties give a definite impression that their main thrust is in the field of mitzvoth between man and God... [A]n image has been created that which identifies Judaism primarily with matters between man and God... The result is that the broad public gets a completely distorted picture of the essence of Judaism, in which the beauty, integrity, and sweetness of the Torah are seriously marred, leaving little in Torah to attract the estranged.
6. The character of a political representative of the Torah community is liable to become blemished. He is asked to negotiate to gain benefits or advantages for the cause of religion, and at the same time he is expected not to turn into a hrose trader. He is forced to resort to flattery, so as to advance himself and obtain a position of pwer, and at the same time he is expected not to become tainted...
There are those who fear that abolishing the religious parties would lead to the end of any political influence for the religious community. On this matter, Rav Yitzchak Hutner told me:Look at the United States. The Jews there have a disporportionately large political influence. Each of the two major political parties competes for their votes; neither of them can do without the support of the Jews. Now imagine there would be a political party "Jews for America" in the United States. It would have absolutely no influence. The same is true here in Israel. If the observant Jews were to join the major parties and work within them, they would have immense influence. Now, separated and concentrated in their own parties, they are quite easily neutralized.