PRINCETON, NJ -- More than half of Republicans and Republican-leaning independents, 58%, do not express a preference when asked in an open-ended format -- with no candidates' names read -- whom they are most likely to support for the party's 2012 presidential nomination. Those who do have a preference most often mention Mitt Romney and Michele Bachmann.

The July 7-10 poll result illustrates the uncertainty surrounding who the Republican challenger to President Barack Obama is likely to be in the 2012 presidential election. The high level of "no opinion" responses suggests that many Republicans are not highly engaged in the campaign to this point, and may be unclear about who is running. It also could indicate that Republicans who are familiar with the GOP field may not yet feel comfortable backing a particular candidate for the nomination.

Gallup typically reads a list of candidate names when gauging nomination preferences. In the most recent update using this closed-ended approach, Romney was the leading candidate. But even with this method, Gallup finds a fairly high degree of uncertainty, with roughly one in five Republicans not having a preference even after being read a list of the likely candidates. That is a higher percentage of "no opinion" responses than Gallup has found at comparable points in prior GOP nomination contests.

Open-ended questions usually produce a higher percentage of "no opinion" responses than do questions in which respondents are offered choices, so it is not unexpected that the percentage with no opinion is much higher than in the closed-ended format.

So while the open-ended format may provide less guidance about current preferences than the closed-ended approach, it does have the advantage of not biasing respondents toward the choices offered. In nomination preference questions, the choices offered are typically the most prominent candidates in the field, which means those questions could underestimate support for less well-known candidates. But the open-ended results from the current poll do not suggest there is a lesser-known candidate excluded from the closed-ended questions who has significant support.

In all, 10 Republican candidates or potential candidates are named by at least 1% of respondents, 8 of whom are official candidates. Gallup includes 9 of these in its closed-ended ballot and in its tracking of candidate name recognition and favorability. The only exception is Texas Gov. Rick Perry -- mentioned by 4% -- who recently said he would reconsider his decision not to enter the race, and is expected to make an official announcement soon. Gallup will provide its initial estimates of Perry's name recognition and positive intensity next Tuesday.

On the other hand, Gallup has tracked the recognition and intensity of former New Mexico Gov. Gary Johnson, but no Republicans in the current poll mentioned his name as the candidate they are most likely to support, casting doubt on whether his candidacy is likely to have an impact on the race.

In addition to Johnson, Michigan Rep. Thaddeus McCotter, former Louisiana Gov. Buddy Roemer, and former Republican strategist Fred Karger are other announced or likely Republican candidates who have lower profiles but have received some media attention. Of these, only Roemer received any mentions in the poll, and in his case it was by just one respondent. Earlier this year, Gallup measured Roemer's recognition (19% average) and positive intensity (average score of 0) and found both to be at low levels.

Implications

Rank-and-file Republicans do not appear to be highly tuned in to the party's nomination campaign at this point, as most are not able to state a preference for their party's 2012 presidential candidate. That to some degree could reflect the slower pace of the 2012 campaign, which has seen most candidates officially announce their candidacies much later than candidates announced in the 2008 presidential election cycle. The 2012 field has taken shape only recently, and it is still possible some prominent candidates such as Sarah Palin, Perry, and former New York City Mayor Rudy Giuliani will run.

Also, to date, there has been just one debate that included something approximating the full field of candidates, held June 13 in New Hampshire, meaning rank-and-file Republicans have had little opportunity to evaluate the candidates in a comparative context.

As 2012 draws nearer and the campaign intensity picks up, Republicans will certainly become more familiar with the field of candidates and eventually settle on their preferred one. But it is clear from available data that the race is wide open.