Federal prosecutors this week indicted former Virginia Gov. Bob McDonnell (R) and his wife on corruption charges. And just like that, another promising Republican star, once touted as a potential presidential candidate who would help the party retake the White House, fell by the wayside.

It's been a rough few weeks for the "deep bench" of possible 2016 candidates that the GOP boasted having in the wake of President Obama's re-election. In addition to McDonnell, New Jersey Gov. Chris Christie (R) has also seen his prospects dim, as he stares down both state and federal investigations into his administration's politically motivated traffic jam scandal.

This is a movie we've seen before. A remarkable number of Republicans floated in the past half-decade as potential party saviors have either fizzled into obscurity or fallen from favor within the party.

To be sure, rampant horse race speculation gives us tons of supposed candidates every cycle, so plenty of the names bandied about in the early going are bound to look silly down the road. But that intense speculation also has another effect, putting leading politicians under the klieg lights of a presidential campaign years before the Iowa caucuses. That scrutiny both forces mistakes and dredges up unsavory details that might not have otherwise come to light.

McDonnell is the most extreme case. Fresh off his gubernatorial election in 2009, he gave the GOP's rebuttal to Obama's State of the Union the following January, an event that elevated his status within the party. Also in his favor: The guy just looked like a typical silver screen president. It didn't hurt that his attorney general, Ken Cuccinelli, famously sued the federal government over ObamaCare when Tea Party enthusiasm was at its peak.

Though McDonnell ultimately opted not to run for president in 2012, Mitt Romney considered him as a potential running mate. And even as late as early last year, some wondered if McDonnell would take a shot at the White House the next time around.

Then McDonnell's shady financial dealings were exposed. Now, the former governor is facing decades in prison if convicted.

Christie's fall hasn't been quite so dramatic, though it's arguably more pertinent to the GOP's future. Though Christie always had a very difficult path to the 2016 nomination due to his moderate leanings, he was nonetheless seen as a more viable candidate than McDonnell due to his proven ability to appeal to voters beyond the GOP tent.

In the early days after his bridge scandal exploded, it seemed like he could pull through. But Christie has since come under further scrutiny, and the federal government announced it is now probing whether he inappropriately used federal Hurricane Sandy relief funds on campaign-style TV ads featuring himself.

As a result, his standing has suffered:

That's a spooky trend line, no matter how you spin it. At the same time, a Quinnipiac poll released this week showed Christie losing ground in a hypothetical matchup with Hillary Clinton.

The list of fallen or falling stars goes on.

There's Sen. Marco Rubio (R-Fla.), whom the GOP turned to last year in hopes that he could alleviate its glaring problem attracting minority voters. With the support of party leaders, he pursued immigration reform, almost instantly eroding his support with the base. He then came off as a flip-flopper by trying desperately to win back his lost conservative cred.

He's quickly fallen from favor with Republican voters, and is now something of a second-tier prospect.

Louisiana Gov. Bobby Jindal (R) had a similarly short run at the top. Jindal was Rubio before Rubio, an ethnic GOPer with an American Dream biography who could theoretically help Republicans make inroads with minority voters. But Jindal's 2009 State of the Union rebuttal received such harsh reviews that he was immediately dropped from consideration as a truly viable candidate.

Jindal is now trying to rekindle interest in his potential candidacy by, among other things, tweeting his support for a reality TV star, and botching the First Amendment in the process.

Safe to say he's not quite the candidate he once was.

Among less-hyped alternatives, Rep. Mark Sanford (R-S.C.) and former Sen. John Ensign (R-Nev.) admitted in 2009 to extramarital affairs, effectively squashing their chances of seizing the party mantle. (Sanford, then South Carolina's governor, has since returned to his old seat in Congress.) And don't forget Indiana Gov. Mitch Daniels, who called for a "truce" on social issues and then bowed out of politics shortly thereafter.

It's tough out there for the GOP's rising stars and presidential "frontrunners." All of which is to say: Look out, Rand Paul.