Persons who have been convicted of offences listed in the Representation of People Act and sentenced to imprisonment of two years or more, unless their conviction has been stayed by a higher court. Such a provision already exists and is being implemented. However, conviction rates in this country being so abysmally low and trials so long-winded, most "criminals" never end up serving a sentence—or if they do, it’s decades after committing a crime. In the meantime, there’s nothing to stop them from sitting in the Union cabinet and lording it over the very officers investigating them. So, here, the critical responsibility lies with the criminal judicial system to speed up matters.
Persons against whom a competent court has framed charges for a heinous or an economic offence attracting imprisonment of five years or more. There’s near-unanimity among those working in the field of electoral reforms that such candidates have to be stopped at the stage of framing charges, as that requires application of the judicial mind. If the police files a fake FIR or cooks up evidence, the case is unlikely to stand scrutiny in a court of law. Charges are framed only if the evidence is compelling enough to prima facie convince the judge that the case is valid. To debar candidates at this stage, a new clause needs to be introduced in Chapter III, Section 8 of the Representation of People Act, 1951. The new provision would allow disqualification of candidates against whom charges have been framed in a heinous offence attracting imprisonment of five years or more.
Persons who are absconding from the law and refusing to join the investigation against them, if the charges levelled are serious enough to attract five years imprisonment. For this too, there would have to be an enabling legislation.