What are the legal provisions? 

• The Representation of the People Act, 1951 (RP Act) provides for law relating to expenditure incurred by ‘leaders of a political party’. These ‘leaders of a political party’ are popularly known as ‘star campaigners’. 
• These star campaigners are usually the top leaders of a political party but can include other celebrities as well. The only requirement is that these persons have to be members of the political party that appoints them. 
• The RP Act provides that a recognised political party (national or State) can appoint a maximum of 40 star campaigners while a registered unrecognised political party can appoint up to 20. 

What are the benefits? 

• The RP Act provides that expenditure incurred by the ‘leaders of a political party’ on account of travel by air or any other means of transport for campaigning for their political party shall not be deemed to be part of the election expenditure of a candidate of such party. 
• The election expenditure limit for candidates is ₹95 lakh per Lok Sabha constituency in larger States and ₹75 lakh in smaller States. 
• Hence, these star campaigners would be vote-fetchers for candidates set up by respective parties without affecting their expenditure limit.

https://www.thehindu.com/news/national/what-are-the-rules-around-star-campaigners-explained/article68095778.ece