No, Prophet Mohammed (peace be upon him and his family) has announced Imam Alis succession and sanctity in several times and situations. The rest goes as follows:
1. When, for the first day, Prophet Mohammad notified limited number of his relatives of his prophecy, in a better world on YOUM O DAR , and after repeating three times, Who is volunteer to believe in my words in order to be my successor?, the only YES response was Imam Alis. Thus, Prophet Mohammad Said You Ali are truly my heritor and successor.
اِنما اَنتَ وصی وَ وارثی
2. When the Emigrants and The Helpers came in to peace by Prophets efforts, Prophet considered Imam Ali as his successor according to the well known tradition MANZALAT tradition, O Ali, you are for me like Aaron for Moses with the exception of not being any prophet afterward.; so Imam Ali was introduced as Prophets successor as Aaron was saint Moses.انت منی بمنزله هارون من موسی الا انه لا نبی بعدی
3. According to the famous tradition-SAGHALIN- which is wildly transmitted for being repeated too many times by Prophet and is accepted for both Shies and Sunni, Prophet has said I leave you with two worthy things: Gods book and my family. If you use these two, you will never be missing leaded after me.انی تارک فیکم الثقلین کتاب الله و عترتی اهل البیتی ما ان تمسکتم بهما لن تزلو بعدی ابداً
4. In verse 59of Al-Nesa:
Obey God, Prophet and your authorities By referring to interpretations, we realize what was meant as authorities is prophets family whose words are apt to be done as Gods and prophets.اَطیعوا الله وَطیعوا الرسول و اولی الامر...
5. In verse 55 of Al-Maede:
Truly, your leader and protector are God, His prophet, and who are believers and giving charity to poor while bending and saying prayers. Based on Shies and Sunnis interpretation the story behind this verse comes back to the time when Imam Ali gave his ring to a poor while bending and saying prayer. Further to this verse, once more again Imam Alis sanctity was proved.انما ولیکم الله و رسوله و الذین آمنو الذین یِِقیمون الصلوة و یوتون الزکوة و هم راکعون
6. In verse 67 of Al- Maede:
Prophet Mohammad! Announce what was sent to you about selecting Ali as your successor or else you have not done Gods mission which was given to you, know that God will protect you from peoples mischief.
The core issue here is Gods knowledge about a group of peoples opposition against Imam Ali as Prophets successor; and since this opposition he had guaranteed prophets security.
In fact, there are many other traditions documents to prove Imam Alis succession except what was just mentioned. Moreover, what makes Ghadir tradition stand out is large amount of Muslims, coming back from Haj, who have been ordered to be witness while Prophet is introducing Imam Ali(pbuh) as his successor.