Republicans’ support for Mitt Romney as their party’s 2012 presidential nominee has increased significantly to 24%, compared with 17% in late May. As a result, Romney has widened his advantage over Sarah Palin in the latest update on rank-and-file Republicans’ nomination preferences.

Going into tonight’s first GOP Presidential debate (without Sarah Palin in the field, by the way), Mitt Romney clearly is the front-runner for the GOP nomination. Unless another candidate emerges, the path to the GOP nomination should be Romney’s to lose.

These results are based on a June 8-11 USA Today/Gallup poll, conducted on the eve of a candidate debate in New Hampshire that will be the first to include some of the better-known candidates.

Romney appears to have gotten a boost in recent weeks after the official announcement of his candidacy. Gallup’s prior update of May 20-24 came just after former co-leaders Mike Huckabee and Donald Trump announced they were not candidates for the nomination; that poll showed Romney and Palin in a virtual tie. Since then, Romney’s support has increased and Palin’s has been flat, leaving Romney with an eight-percentage-point advantage.

That is the largest numerical lead Gallup has measured for any candidate since it first began measuring nomination preferences in September. In that initial September poll, Romney held a seven-point advantage over the field of candidates. Romney or Huckabee held slim margins of no more than four points in subsequent polls.

No candidate besides Romney has shown a significant increase in support since the May update, though Rick Santorum, who also recently announced his official candidacy, saw his support rise from 2% to 6%. Meanwhile, support for Newt Gingrich, whose campaign has been off to a rocky start since his official announcement last month, is now at 5%, a slight decline since May. The high point for Gingrich was 13% in November.

And, Romney’s lead over the field expands with Sarah Palin out of the field.

Let’s look at the graph:

Note with Sarah Palin gone, Michele Bachmann does not rise substantially in the polls with Palin voters being redistributed throughout the field. However, Bachmann will stick in Iowa and be able to gain momentum there. Whereas, this is a national poll.

What are the demographics of the GOP voters?

The graph:

So, what does this all mean?

Mitt Romney is the early front-runner and the only challenger who is close in the polls is Sarah Palin, who has not decided whether to run or not. A number of candidates remain in the field but their chances of winning the nomination appear remote.

Perhaps tonight’s GOP Presidential debate will deliver some momentum to the third and fourth tier candidates. But, I doubt it. This race is Romney’s to win or lose.

Romney may be emerging as a front-runner in a GOP race that has been characterized to date by its lack of a leading candidate. Republican nomination contests usually have a clear front-runner, and that candidate often goes on to win. But that did not hold true in the last presidential election cycle, when Rudy Giuliani led in national preference polls throughout 2007 but performed poorly in the actual nominating contests in 2008. Additionally, even if Romney were to expand his lead into the double digits in the coming months, he still would rate as one of the weakest Republican front-runners in recent GOP nominating history.

Romney remains behind lesser-known candidates Cain and Bachmann in Gallup’s measure of positive intensity toward candidates, though his score seems to be on the rise.

Whether Romney is actually assuming the mantle of the front-runner will be clear in future polls. The current results could be a short-term bounce due to increased attention paid to his campaign after his official entry into the race, or could indicate a more lasting shift in preferences that has put him in the top position in the GOP field.