The third major GOP presidential endorsement from a daily South Carolina newspaper has again gone to Sen. John McCain. The Myrtle Beach Sun News announced Wednesday that it is backing the Arizona senator because he represents “the GOP’s best hope of keeping the presidency.”  South Carolina’s largest paper, The State, and the Greenville News have also thrown their support behind McCain.

In the editorial, the Sun News laid the case for McCain not only because he is “the only Republican candidate who could win in November,” but because he “would be a competent president.”

He understands that America must root its foreign policy in robust diplomacy and vigorous, well-trained, well-deployed military forces. He understands that federal spending restraint is the key to relieving the economic misery of the American middle class, that massive new open-ended entitlement programs would be a mistake. And he knows how to work across party lines to forge compromises that work well for the American people. He could be successful from Day 1 in office.

The other Republican candidates would have difficulty prevailing in a general election and, presidentially speaking, are unknown quantities. [...]

S.C. voters were unkind to McCain in his 2000 presidential run. This time, they can – and should – anoint him the Republican establishment candidate, in hope that GOP voters in the big states holding primaries Jan. 29 and Feb. 5 will cement the deal. McCain represents their best hope of retaining the presidency and retaining a sane political balance in Washington. He earns The Sun News recommendation. [Myrtle Beach Sun News]

But what is the impact of all these endorsements?  The only way we’ll really know is on Saturday.  If McCain ends up winning this state, then a lot could be said for what is so far a clean sweep of editorial-board support.

And having three of the most well-read dailies in the state on your side really can’t hurt either way.