Regular Fox News Channel viewers can get ready to miss Alan Colmes — as in “Hannity & Colmes” — after this week’s announcement that the liberal half of the liberal-conservative duo is leaving the show at the end of the year. Co-hosted by Colmes and Sean Hannity for 12 years, the show is top-rated in its time slot, a tribute to the chemistry the two have developed arguing all sides of national political issues. Colmes, known for deft, left-of-center counterpunches to Hannity’s leading role, decided it was time to do something different, according to reports. He plans to continue as a commentator on a variety of Fox News shows while also hosting his radio program. The “Fair and Balanced” network said Colmes also will develop a weekend program. No word yet on a new sidekick for Hannity.