Barack Obama has been careful to avoid obvious hints as to his choice of running mate, forcing pundits to assemble the smallest of clues. This week, one-time frontrunner Virginia Governor Tim Kaine saw his chances fall dramatically when his predecessor, Mark Warner, was assigned to give the keynote Convention speech; Obama is not likely to want two prime-time speeches from Virginia political leaders. Indiana Senator Evan Bayh also saw his chances decline, as a strong progressive backlash emerged against his zealous support for the Iraq War. The fact that both Clinton’s have been given prime-time convention speeches also decreases the likelihood that Obama will choose Bayh, a Hillary Clinton backer. Kansas Governor Kathleen Sebelius is scheduled to speak Tuesday night, which would be unnecessary if she were to speak on Wednesday as the VP choice. This leaves Delaware Senator Joe Biden as the most likely choice, and – at this point – the most acceptable for progressives.

After George H.W. Bush won the 1988 election with the unqualified Dan Quayle as his running mate, the theory that VP choices made a difference appeared to go out the window. Nevertheless, we all remain eager to interpret what a candidate’s choice of running mate says about their judgment and/or ideology.

Evan Bayh and Tim Kaine

In that vein, progressives have been extremely alarmed over talk that Indiana Senator Evan Bayh was among the top-tier choices. President Bush publicly praised Bayh for his aggressive support of the Iraq War, and his choice would send shockwaves through Obama nation.

Progressives also expressed alarm over Virginia Governor Tim Kaine. Kaine went seemingly overnight from favorite to an also-ran, and the choice of Mark Warner to give the convention keynote is seen as confirming he will not be Obama’s pick.

One caveat here: Who would be bothered if the former and current governors of Virginia both speak in prime-time? Given the close personal relationship and similar backgrounds of Kaine and Obama, his selection is still feasible.

Kathleen Sebelius

While the Kansas Governor remains the popular choice among progressives, she has been given a Tuesday night speaking slot and is no longer seen as a likely choice. She has also already been rewarded for her support of Obama by being named Convention chair.

Bill Richardson

Long considered politically untouchable due to the Clinton’s description of him as a “traitor,” Bill Richardson would shatter the conventional wisdom and put a Latino on a national ticket for the first time. I was struck by the lack of Latinos on the convention speaker list, with former Denver mayor Federico Peña the only long-scheduled speaker from this politically potent constituency.

Los Angeles Mayor Antonio Villaraigosa, who backed Clinton but now enthusiastically campaigns for Obama, is not a scheduled speaker. But perhaps Obama’s campaign also realized this Latino deficit, as yesterday they gave a slot to Richardson and another to Colorado’s Latino Senator, Ken Salazar. The addition of these prominent Latino speakers likely kills Richardson’s chances.

Biden: The Likely Choice

Here are the clues leading to Joe Biden: he is Catholic, has strong foreign policy experience, has proved willing to go after McCain on Obama’s behalf, does well with white working class voters, has no future presidential ambitions, would be loyal to Obama, and the two get along quite well.

Most importantly, Biden has kept uncharacteristically quiet in recent weeks, whereas he frequently served as an Obama surrogate prior to this time. When Biden is quiet, something is afoot.

The downsides: talks too much and too freely, opening the ticket up to the “gotcha” moments that the media loves. Many find him boring. After over two decades in office, few can point to major Senate accomplishments.

Two best reasons progressives should cheer Biden’s selection: (1) we avoided Bayh, (2) when the media reminds everyone about Biden’s “plagiarism” of a British politician’s speech in 1987, and Republicans try to benefit from this, the media can also discuss what John McCain was up to in that same period—namely, the Keating Five scandal that implicated the Republican nominee in the Savings and Loan debacle that cost taxpayers billions.

The Wild Card

These crafty Obama folks announced late yesterday that Biden, Bayh and Richardson would all be speaking on the night highlighted by the VP’s speech. This means that Tim Kaine is the only top-lister not otherwise scheduled to speak.

Obama will likely announce his choice early next week.