Politico follows up this morning on Karl Rove’s assertion that Rick Perry’s big entrance into the Republican presidential sweepstakes might prompt more potential candidates to toss their hats in the ring.  Could we see names like Rudy Giuliani and Chris Christie generate the same kind of big splash we saw this week with Perry?

A candidate who joined the race at such a relatively late date would face daunting prospects, with time running short to launch an organization and some bundlers who had been on the sidelines moving toward Perry, whose supporters argue is the one who can best unite a party fractured into Tea Party and establishment camps. But in a volatile year, some top Republicans believe it’s possible that another heavyweight candidate—such as Sarah Palin, Christie, Ryan or even Rudy Giuliani—could still join in.

While Christie continues to maintain that he is not running, Palin continues to leave the door open. Giuliani, who was endorsed by Perry in his 2007 presidential race, has made clear he is still weighing a campaign, and has said it would focus centrally on New Hampshire. He has put a time frame of deciding by the fall.

Ryan, the Wisconsin congressman who is beloved among fiscal conservatives and the Republican intelligentsia, has made some conservative hearts flutter for months—most notably writer William Kristol. His fans argue that despite his connection to the Medicare revamp proposal that Democrats have been using to thump Republicans as “extreme” in swing states, he is proven voice who has shown he can stand up to President Obama.

Allahpundit and I wrote about the reasons why we think Ryan should stay in the House yesterday, so I won’t restate the entire argument here, but there is one more consideration.  While Ryan is well-liked and respected, he doesn’t exactly have a nationwide following — or even a statewide following in his own Wisconsin.  The conservative intelligentsia might swoon over a Ryan run, but he will have the same problem that every House member has, which is a lack of a solid, broad constituency.  Only Michele Bachmann’s Tea Party activism sets her apart, and Ryan would have to eat into that rather than find a separate and competing base of support.

Christie has said rather bluntly that he’s not running for President, telling the media that only a suicide would get them to stop asking about it.  It’s hard to walk that back, but also difficult would be transforming two years of a first term as a governor of blue New Jersey into a presidential race.  His neighbor, Rudy Giuliani, can lay claim to having a national draw, but Giuliani is also older, both in age (67) and in political terms. He ran in 2008 as an establishment moderate, which is precisely the wrong person to excite the base now — and is territory covered, willingly or not, by Mitt Romney in both respects.

The only person left on the sidelines at the moment who would be a gamechanger is Sarah Palin — and Perry’s entry limits that in at least to small degree.  Palin campaigned for Perry in Texas in his re-election bid, and their political positions are close enough that there isn’t much contrast Palin could draw now that Perry has entered the presidential sweepstakes.  Palin has a nationwide following, many of whom have been backing Bachmann and the rest now running to Perry.  The big difference is that Palin could almost immediately organize and raise money — an ability that the other candidates above might find difficult to do this late in the process — if she wants to run.  Having scheduled an early October event with Glenn Beck, she’s cutting the fundraising and organizing time to a mighty thin slice before the Iowa caucus.  And Perry is already moving to secure the big-ticket donors on the Republican sidelines, a process that will be all but over by the time Palin takes the stage in October.

Perry’s big splash certainly might have other Republicans saying coulda woulda shoulda.  But other than Palin, none of them have a good enough position to overcome the fundraising and organizing disadvantages they will face with Perry now in the race, and the clock is ticking on Palin.