At least two well-known Republicans are actively considering challenges to Democratic Sen. Mark Begich, who enters the 2014 cycle as one of the most endangered incumbents.

According to Republican insiders in the state, Lt. Gov. Mead Treadwell and 2010 Senate nominee Joe Miller are making calls and lining up support for potential Senate bids. Former Lt. Gov. Loren Leman and Anchorage Mayor Dan Sullivan are also viewed as potential Begich challengers. Gov. Sean Parnell might be interested as well, insiders said.

GOP consultant Andrew Halcro said it might be easier to ask which Republicans aren’t considering taking on Begich. But, he added, Begich will be more difficult to defeat than most think after striking a moderate tone and working hard during the past four years.

Begich is running for his first re-election. In 2008, he defeated Republican incumbent Ted Stevens, one week after Stevens was found guilty of corruption charges in federal court — a ruling that was thrown out five months later. Begich, then mayor of Anchorage, won by less than 4,000 votes.

GOP presidential nominee Mitt Romney carried Alaska last week by 13 points.