Petering out in a show of bonhomie

Samajwadi Party on Monday was engulfed in a feud as defeats in bypolls in Mulayam Singh Yadav's stronghold continued to create rumblings. The day started with SP general secretary Amar Singh's interview to a newschannel raising speculation if he was quitting the party and ended with the tension petering out in a show of bonhomie and promise of loyalty.

I know peter out means "to become weak" and bonhomie means "friendliness" but still I can't understand the underlined parts.