It is not simply Rep. Paul Ryan (R-Wis.) who is generating speculation about a late entrance into the Republican presidential primary race. Politico reports:

The Texas governor’s late entry in the presidential race might have been expected to close out the GOP’s 2012 field. But, in some conservative circles at least, there’s evidence it’s had the opposite effect.

Rather than marking the end of the period in which new candidates would join the race, it may have touched off a new phase of interest in the contest by suggesting that the unsettled GOP field still has room for more candidates.

In part that desire for fresh faces stems from unease with Texas Gov. Rick Perry. His attack on Ben Bernanke, his back-peddling on his controversial mandate to vaccinate schoolgirls against human papillomavirus and the realization that he sure does seem very Texan (and hence potentially limited in his national appeal) have unsettled some Republican insiders and activists. Karl Rove on Fox last night put it this way:

“It’s his first time on the national stage, and it was a very unfortunate comment. You don’t accuse the chairman of the Federal Reserve of being a traitor to his country and being guilty of treason and suggesting that we treat him pretty ugly in Texas — that’s not, again, a presidential statement.”

More worrisome than a single gaffe, Rove says, is the image Perry is reinforcing, “It’s not smart politics, either. Governor Perry is going to have to fight the impression that he’s a cowboy from Texas. This simply added to it.”

Perry defenders, taking on a certain defiance characteristic of devoted Sarah Palin fans, insist this is all about nothing or simply griping from supporters of President George W. Bush. But for those (including big donors, state party leaders and Republican activists desperate to win back the White House) not inclined to accept ad hominem attacks in lieu of political analysis, those excuses are unconvincing. (Note to the conservative blogosphere: Simply dismissing every messenger as a pawn of the MSM or driven by ulterior motives may be emotionally satisfying but it’s politically self-defeating.)

But the willingness to continue searching for other presidential choices also reflects how easily Perry has stepped into the fray and zoomed into the top tier of candidates. In short, Perry has demonstrated that there is a reason to keep looking for other candidates and that it’s not too late for others to scramble on board.

In addition to Ryan, some conservatives still yearn for Gov. Chris Christie to join the race. His ongoing and public dissatisfaction with the field leads some to conclude he might step into the race himself. But there is as yet no sign he is organizing, reaching out to donors or seriously evaluating a presidential run.

We should not forget Mitt Romney, who is taking on the role of the nice-guy, best friend in a romantic comedy. The potential suitors turn out to be flakes or cads, and the audience begins to wonder, “Well what about that guy?” It is possible that the other candidates will implode, newcomers won’t materialize and a large chunk of the GOP electorate will drift back to Romney. (“Romney’s supporters believe that the Bay Stater’s tortoiselike strategy will play to one of his essential strengths — durability over the long haul — and show Republican primary voters that he’s best prepared to go up against a vulnerable incumbent president,” Politico says.) That’s what he and his team hopes, at any rate.

At some point, the window of opportunity will shut for new candidates, and voters will have to pick from the best of the lot. But for now, many Republicans are still asking: Can’t we do better than this?