Anjana Pasricha NEW DELHI — India's election spending is set to reach $5 billion as candidates spend millions of dollars on what studies say will be the country’s most expensive campaign. Analysts say a large portion of funding comes from unaccountable sources, and some is used to bribe voters. This campaign season is a financial boon for many businesses — particularly advertisers, helicopter and car lease companies, and those printing campaign posters and flags. India main opposition Bharatiya Janata Party leader Harsh Vardhan, center, flashes a victory sign as he arrives with party nominee Mahesh Giri, left, to file Giri’s nomination papers for the upcoming…