WASHINGTON — A new poll suggests that Sen. Susan Collins’ approval rating is at or above 60 percent among Republicans, Democrats and independents – a rare trifecta that puts the Republican on safe-looking ground as she looks ahead to 2014, the pollsters said.

But the survey team at Public Policy Polling said Collins could still face a viable challenge from a hypothetical, unnamed “more conservative” candidate in the Republican primary.

PPP reported Thursday that Collins had a 63 percent approval rating among the 1,268 Maine voters who participated in the firm’s telephone survey last week. Her support was highest among self-identified Republican voters, who gave her a 66 percent approval rating. But independents were not far behind at 64 percent, and even 60 percent of Democrats approved of Collins’ performance.

A moderate Republican, Collins was first elected to the U.S. Senate in 1996.

The poll results suggest that Collins would handily defeat Democratic U.S. Reps. Mike Michaud and Chellie Pingree, leading them by 18 and 25 percentage points, respectively. Neither Michaud nor Pingree have indicated plans to challenge Collins, although their names are occasionally mentioned as potential Democratic candidates both in that race and in Maine’s 2014 gubernatorial race.

Faced with a serious Republican primary challenger, however, Collins may not fare as well, PPP predicted.

Collins’ lead shrank to just 3 percent among Republicans when asked whether they would support the senior senator or a hypothetical, “more conservative” primary challenger. And 75 percent of those identifying themselves as “very conservative” indicated they would like to replace Collins. But Republicans may have trouble keeping the seat in such a case, just as Republicans lost the seat held by retired Sen. Olympia Snowe last November.

“This seat looks pretty safe for the GOP if Susan Collins is its candidate next year,” Dean Debnam, PPP’s president, said in a news release announcing the results. “But if she’s not — either through retirement or a primary challenge — it could be very hard for the Republicans to hold on.”

Washington Bureau Chief Kevin Miller can be contacted at 317-6256 or at:

kmiller@mainetoday.com