ROME (Reuters) - Pope Benedict's resignation could limit the chances of former Italian prime minister Silvio Berlusconi closing the gap on the center-left frontrunner before this month's election, some pollsters and analysts say. Berlusconi, who seemed certain to lose a few months ago, has staged an aggressive campaign based on tax-cut promises that has eroded the lead of Pier Luigi Bersani's Democratic Party (PD) and raised the prospect of an inconclusive outcome. ...