A weakened advertising picture, including a lack of political advertising spending, weighed on a pair of station groups that reported earnings Tuesday.

Nexstar Broadcasting Group, which owns 46 television stations, reported that it swung to a second-quarter loss of $20.9 million, compared with a year-earlier profit of $1.2 million. Revenue slipped more than 5 percent to $57.9 million.

The declines come as the company sees weakness in core advertising categories and at its NBC affiliates, which are affected by the prime-time ratings declines plaguing the network. The company also attributed the results to the absence of $3.5 million in political advertising spending.

The lack of political advertising revenue was also a factor for Liberty Corp., the South Carolina-based owner of 15 network-affiliated stations. Unable to offset the absence of $3.4 million in political advertising revenue, Liberty reported a 3 percent revenue decline, but was able to more than double its second-quarter profit to $8.3 million from a year-earlier profit figure of nearly $3.1 million.

The company noted that the 2004 quarter included a $6.9 million charge related to a company investment, while the 2005