Look at the underlined part?

Look at the underlined part  The Prime Minister, while describing Anwar as a “poor loser”, has called for “national reconciliation”. But it may take some time for politics in the country to stabilise and the animosities that have been unleashed to abate. The police have reported that  there were more than 1,400 violent incidents sinc e the campaign for the elections began. My question is here simple past has been used with since.I think past perfect should have been used.Am I right?If not,then please tell me why? Thank you.