You’d think a relatively well-known, long-serving senator from an early primary state would be given some respect by 2016 handicappers. But Lindsey Graham of South Carolina, who on Thursday formed a committee to explore a run for president, is not even listed on Betfair. To put that in perspective, Jon Huntsman, Carly Fiorina and Donald Trump are all listed.

Why is Graham considered such an unlikely Republican nominee (by everyone except Sen. John McCain, that is)?

First, Graham is a creature of Washington in a year when Republicans are looking outside the capital. Graham has served in the Congress for 20 years (12 in the Senate and eight in the House). Every other plausible GOP nominee either serves outside of Washington or has been in Congress for just a few years (Ted Cruz, Rand Paul, Marco Rubio).

According to a Pew Research Center poll conducted last year, 51 percent of Republicans would rather their 2016 nominee to be a governor than a member of Congress. That’s up from 2007, when just 32 percent did, and might help explain why McCain — a close friend of Graham’s — was able to capture the GOP nomination in 2008. Even worse for Graham is that just 15 percent of Republicans say being an elected official in Washington for many years makes them more likely to vote for a candidate, while 36 percent say it makes them less likely. In 2007, it was 40 percent more likely and only 18 percent less likely.

Graham, simply put, is the wrong candidate for the current mood of the Republican Party. McCain won in a much different environment.

Second, the Republican voters who know Graham best aren’t exactly enamored with him. If Graham expects to overcome his party’s mind-set, he’d probably need to unleash some combination of charm and political skill. He hasn’t demonstrated an ability to do that.

Graham won his 2014 Republican primary against weak competition with just 56 percent of the vote. Sen. Tim Scott, South Carolina’s junior senator, romped through his primary with 90 percent of the vote. Now, it’s true that Graham is more moderate than Scott, but that doesn’t come close to explaining their massive percentage of vote differential.

In the 2014 primary season, I built a three-variable model that sought to inform us why certain Republican incumbent senators did better in primaries than others by looking at the partisan tilt of the state, the ideology of the senator, and how “establishment” he or she was. All else being equal, more moderate and more establishment Republican incumbents do worse. GOP incumbents are also more likely to perform poorly in redder states.

Controlling for these three factors, Graham earned 21 percentage points less of the vote than expected. Of the 31 incumbent Republican senators that have ran for re-election in the Obama era, only Thad Cochran of Mississippi, John Cornyn of Texas and Richard Lugar of Indiana did worse than the fundamentals suggested. In other words, Graham was a far-below-average candidate.

Lastly, there is no sign Republicans nationally like Graham a lot either. Besides coming in last place with 0 percent of the vote in a YouGov poll this month, Graham’s net favorable ratings (favorable minus unfavorable) are also quite weak. In an average of January YouGov surveys, Graham’s net favorable rating was +17.5 percentage points, with 58.5 percent of Republicans being able to form an opinion of him. That’s not a good ratio. Only Chris Christie and Sarah Palin are further below expectations among the plausible 2016 candidates.