Some individuals try to say the word Al-Naas in the verse refers to the infidels and say the following matching sentence (inna allah la yahdi al-qowm al-kafirun) too, attests to this claim, the meaning thus expressed is not what the word "al-naas" signifies. Al-Naas refers to both infidels and believers and there is no exclusive connotation in it to refer to infidels only. Therefore, the word "al-kafirun" might refer to a degree of infidelity that includes infidels of the time of Prophet (PBUH) on whom he has expressed fear in his heart.
The two words of iblagh and tabligh are infinitives of ef'aal and taf'eel paradigms from the Arabic roots of belagh and bolugh, meaning delivery of a message, maturity, reaching something, close to reaching something, or finalization of something.
In the holy Verse of Proclamation the words bolugh and belagh have been used in their infinitive meanings in taf'eel paradigm to signify conveying. There is no difference in meaning between iblagh and tabligh, except that tabligh is more emphatic than iblagh in conveying a message. This is because adding new letters to a word suggests new meanings for that word.
Shia Muslims believe that the Verse of Proclamation clearly refers to the leadership of Imam Ali (A.S). They say "that which has been revealed to you from your Lord" is applicable to the leadership of Imam Ali (AS) because:
First: The Almighty God has shown much diligence in this case, so that if it is not announced, the path of prophetic mission will be unfinished. This is nothing other than the issue of imamate, leadership of Islamic Ummah and succession of Imam Ali (A.S), who is responsible for all duties and authorities of the Prophet (PBUH) except Revelations.
Second: The verse suggests that announcing the Order was difficult for the Prophet (PBUH) and he feared that people might not obey what has been requested, and they might stir disputes and discords to destroy his 23 years of attempts in the cause of Islam. Given the date of the event, there is no doubt that the Verse of Proclamation has been revealed to refer to the leadership of Imam Ali (A.S).
source : www.tebyan.net