- UP's Gorakhpur is the seat that Chief Minister Yogi Adityanath held for five terms. He vacated it last year after becoming chief minister, following the BJP's sweep of the 2017 assembly elections, capturing 325 of the 403 assembly seat along with allies. Phulpur was vacated by his deputy Keshav Prasad Maurya.
- Regional heavyweights and arch rivals Samajwadi Party and Mayawati's Bahujan Samaj Party have pooled resources to take on the BJP in Gorakhpur and Phulpur in what is seen as an experiment to test the ground for a larger alliance in the 2019 national election.
- Yogi Adityanath campaigned hard in both constituencies and described the by-elections as a dress rehearsal for the general election next year. "Our victory margins will be as big as in 2014," he told NDTV. There was 47 per cent polling in Gorakhpur last week, and 38 per cent in Phulpur.
- In both seats, the Samajwadi Party is the BJP's main challenger, with the BSP offering support in a rare deal that includes the Samajwadi Party's support for the BSP in Rajya Sabha elections in UP later this month. "If we win, there will be a bigger alliance," promised Pravin Nishad, fielded by the Samajwadi Party in Gorakhpur.
- Mayawati, seen as the Dalit powerhouse in the state, has not fielded a candidate. Her workers have asked the sizeable Dalit community to vote for the Samajwadi candidates, though she has not committed to a bigger partnership, waiting to see how the experiment works. The present arrangement, she has insisted, is an "agreement" not an "alliance."
- Both the Samajwadi Party and the BSP attended a dinner party hosted by the Congress' Sonia Gandhi in Delhi last night, seen as an attempt to consolidate opposition unity ahead of the 2019 national election. In the UP by-elections however, the Congress has fielded its own candidates.
- The Bihar by-elections are seen as a referendum on Chief Minister Nitish Kumar's decision last September to dump Lalu Yadav and the Congress to partner with the BJP. The RJD has accused Mr Kumar of backstabbing voters who chose the Grand Alliance of the RJD, Nitush Kumar's Janata Dal (United) and the Congress in 2015.
- Nitish Kumar, who campaigned extensively for the BJP and Janata Dal UNited candidates, defended his decision in public speeches stating that he allied with the BJP in the interest of the state.
- With Lalu Yadav in jail in a corruption case, his son Tejashwi Yadav fronted the RJD's campaign in Bihar and these by-elections are also seen to test his leadership.
- The RJD, already in alliance with the Congress, is fighting these by-elections with new friends by its side - Dalit leaders Jiten Ram Manjhi and Anil Kumar Sadhu, who is also Union Minister Ram Vilas Paswan's son-in-law.