Mitt Romney on Friday became the latest member of the GOP's class of 2012 presidential candidates to call for an increase in the minimum wage. In doing so, he joined Tim Pawlenty and Rick Santorum.

Meanwhile, when a Democratic bill increasing the minimum wage to $10.10 an hour came up for a vote in the Senate last month, all but one Republican voted against even proceeding to a vote on it. And basically no major Republicans in Congress are joining the cause of the trio above.

So what's up? Why are former GOP presidential candidates increasingly united on this issue even as their party's congressional contingent is clearly not ready to heed their calls?

A few things:

1. Being a former presidential candidate is easier than being a current member of Congress.

It's much easier to speak your mind when you don't necessarily have another campaign to consider. That's definitely the case with Pawlenty and appears to be true of Romney -- although some supporters won't let go of the idea that he could try again in 2016.

People in such a position are often interested in doing the right thing for their party as a whole. And given that a minimum wage increase polls extremely popularly, it shouldn't be too surprising that a few Republican graybeards are starting to push their party in this direction.

The same thing is happening with immigration. While many Republicans who are out of office agree that their party should pursue comprehensive reform, few in Congress have shown an appetite for sticking their neck out and (to their minds) risking their careers.

For the risk-averse politician -- which is basically a redundant phrase -- taking a stand when you have to worry about your next campaign isn't an easy call. A big reason the GOP opposes minimum wage increases is because the business community opposes them. And nobody wants to be the first GOP lawmaker to run afoul of those folks.

2. It fits with their messaging.

Santorum is one exception when it comes to running another campaign. He has made it patently obvious that he's likely to run for president again in 2016.

He has also made it pretty clear, if you just look at the cover of his new book, that he aims to do so as the candidate of "Blue Collar Conservatives." And what better way to find favor with such working-class Republicans than to be among the first in your party to back a minimum-wage hike?

Santorum, to put it plainly, is a long shot, and the more he can build a real niche, the better.

The message also makes a lot of sense for Romney and Pawlenty.

Pawlenty has long hailed his blue-collar roots -- he calls it "Sam's Club Republicanism" -- and he even signed a minimum-wage increase into law as governor of Minnesota (while vetoing a later one).

And then there's Romney, who faces the fact that the lasting image of his 2012 campaign is still his "47 percent" video. The more Romney can do to mend fences with working-class voters and look more populist, the better for him and his legacy.

3. It's not unthinkable that the GOP could get on board

These three comments feel a little like trial balloons, and the reaction they earn — or don't earn — could conceivably embolden other Republicans to gently inch toward supporting a minimum-wage increase.

As Think Progress notes, about one-quarter of Republicans in Congress have been supportive of at least some type of minimum-wage increase in the past. And polls show the GOP base is split about 50-50 on this issue. So it's not like this is a third-rail situation where it would be unheard-of for a segment of congressional Republicans join with Democrats to work something out.

The question is whether Republicans who might be open to a hike think this is the right time and the right amount.

Proponents of the minimum wage regularly argue that it hasn't kept pace with inflation. That might not be compelling to Republicans, though, given that the wage (in 2012 dollars) is still above where it was in the 1980s and 1990s.

And then there's the matter of the recent Congressional Budget Office report, which estimated that upping the minimum wage would increase the wages of 16.5 million Americans but cost half a million jobs.

That latter figure will certainly temper any GOP support for a minimum-wage increase — or at least the specific increase that Democrats are proposing (which CBO reviewed). But it's also not as if Republicans have forcefully made the case that this is the wrong approach. Instead, they've pretty quietly opposed it.

That suggests there could be room to working something out — whether today or in the next few years.