First there are many Islamic opinions which consider Democracy to be Shirk.
An excerpt from the fatwa at Islamqa says:
Undoubtedly the democratic system is one of the modern forms of shirk,
in terms of obedience and following, or legislation, as it denies the
sovereignty of the Creator and His absolute right to issue laws, and
ascribes that right to human beings. Allaah says (interpretation of
the meaning):
“You do not worship besides Him but only names which you have named
(forged) — you and your fathers — for which Allaah has sent down no
authority. The command (or the judgement) is for none but Allaah. He
has commanded that you worship none but Him (i.e. His Monotheism);
that is the (true) straight religion, but most men know not”
[Yoosuf 12:40]
“The decision is only for Allaah”
[al-An’aam 6:57]
But the same fatwa also quotes another scholar which hold elections obligatory with the only intention to establish the Shariah, by appointing a Shariah friendly member:
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) was
asked about the ruling on elections, and he replied: I think that
elections are obligatory; we should appoint the one who we think is
good, because if the good people abstain, who will take their place?
Evil people will take their place, or neutral people in whom there is
neither good nor evil, but they follow everyone who makes noise. So we
have no choice but to choose those who we think are fit.
So based on the above fatwa , if there is such a legislation to establish Islam as a national religion than Yes it is obligatory to support it and those (even among the Muslims) who oppose it would be approaching Kufr.
A relevant fatwa was asked, from which it is very clear that it is an obligation to support all such endeavor , there should not be any fear of political correctness to achieve this :
As you know, here in Algeria we have what are called legislative
elections. There are parties which call for Islamic rule, and there
are others that do not want Islamic rule. What is the ruling on one
who votes for something other than Islamic rule even though he prays?
They replied:
The Muslims in a country that is not governed according to Islamic
sharee’ah should do their utmost and strive as much as they can to
bring about rule according to Islamic sharee’ah, and they should unite
in helping the party which is known will rule in accordance with
Islamic sharee’ah. As for supporting one who calls for
non-implementation of Islamic sharee’ah, that is not permissible,
rather it may lead a person to kufr, because Allaah says
(interpretation of the meaning):
“And so judge (you O Muhammad صلى الله عليه وسلم) among them by what
Allaah has revealed and follow not their vain desires, but beware of
them lest they turn you (O Muhammad صلى الله عليه وسلم) far away from
some of that which Allaah has sent down to you. And if they turn away,
then know that Allaah’s Will is to punish them for some sins of
theirs. And truly, most of men are Faasiqoon (rebellious and
disobedient to Allaah).
- Do they then seek the judgement of (the days of) Ignorance? And who is better in judgement than Allaah for a people who have firm
Faith”
[al-Maa'idah 5:49-50].
Hence when Allaah stated that those who do not rule in accordance with
Islamic sharee’ah are guilty of kufr, He warned against helping them
or taking them as allies or close friends, and He commanded the
believers to fear Him if they were truly believers. He says
(interpretation of the meaning):
“O you who believe! Take not as Awliyaa’ (protectors and helpers)
those who take your religion as a mockery and fun from among those who
received the Scripture (Jews and Christians) before you, and nor from
among the disbelievers; and fear Allaah if you indeed are true
believers”
[al-Maa’idah 5:57]
And Allaah is the Source of strength. May Allaah send blessings and
peace upon our Prophet Muhammad and his family and companions. End
quote.
Standing Committee for Academic Research and Issuing Fatwas
Shaykh ‘Abd al-‘Azeez ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh
‘Abd-Allaah ibn Ghadyaan
Fataawa al-Lajnah al-Daa’imah (1/373).
Allah knows best