We’ve seen this dynamic before. Months into a presidential nominating contest, the party’s base and establishment have gotten a good look at their candidates, and find themselves underwhelmed, if not dismayed. They suddenly realize they don’t much care for the field, start to feel antsy, and wonder if there’s a savior candidate available to rescue the party before it’s too late.

With Texas Gov. Rick Perry (R) launching his presidential campaign this weekend, we have the latest in the series of savior candidates. As Josh Green recently noted, however, the track record for these presidential hopefuls is poor.

In the past, notable figures — from actor and former Tennessee Senator Fred Thompson to General Wesley Clark to the late Massachusetts Senator Ted Kennedy — all aroused the same rapturous excitement and outsized expectations that Rick Perry is awakening now. But none of them remotely lived up to the hype.

That’s the paradox of the last-minute savior. The attention and enthusiasm are alluring, the possibilities are enticing, the path to the nomination tantalizingly clear. But each time, the lesson has proved the same: latecomers always lose.

As Perry’s effort gets underway, it’s worth pausing to ponder two questions: why do latecomers always lose and will Perry be any different?

The first question is easier. Savior candidates invariably falter because running for president is infinitely more difficult than it looks. When one’s rivals have months of lead time, it’s not just a matter of catching up in polls and fundraising; it’s also a matter of immediately reaching mid-season form. The other candidates, in other words, have had more practice being candidates.

Consider an example. In April, Mitt Romney spoke at a cattle call in New Hampshire, hosted by the Koch-financed Americans for Prosperity. It was billed as Romney’s unofficial debut as a 2012 candidate — and he was awful. His speech was weak, his Q&A was awkward, and his message was disjointed. Romney was, objectively, a bit of a mess, even joking about “hanging” President Obama before quickly walking it back.

How is this relevant? Because few even remember this appearance now. It happened away from the spotlight, without the intense glare of a national campaign in full swing, when Romney had the luxury of slipping up before sharpening his message.

And that’s a luxury latecomers never have. Every candidate needs time to get better — on the stump, in interviews, in debates, in engaging with diverse national voters directly — but so-called saviors are forced to be polished and proficient immediately. They don’t have time to work the kinks out, and when they slip up, as everyone does, it garners significantly more attention, and does far more damage.

Will Perry run into the same trouble? We’ll obviously find out soon enough, but I’d argue the Texas governor is probably better suited than the other modern latecomers. Clark had never sought elected office and it showed; Kennedy couldn’t say why he was running; and Thompson was just incredibly lazy. Perry, meanwhile, is a sitting governor of a large state who’s won three statewide races in the last nine years, and appears to understand what’s expected of a national candidate.

He’ll have to be very good, very quickly, to avoid the other savior candidates’ fate, but I wouldn’t write Perry off just because he’s late to the game. The current GOP field really is weak, and Perry may very well prove to be the one candidate who can appeal to all of the party’s key constituencies.

If he can avoid rookie screw-ups, I suspect it’ll be a three-person contest for the nomination: Romney, Bachmann, and Perry.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.