A group of centrist Democratic senators held their first meeting this week to discuss brewing -- but so far non-specific -- concerns with President Obama's budget.

Many of these emerging Democratic budget skeptics also fought to slim down the economic stimulus bill before it became law next month: Sens. Ben Nelson (NE), Mary Landrieu (LA), Evan Bayh (IN), Mark Begich (AK), Amy Klobuchar (MN), and others were part of influential centrist blocs during the stimulus debate and are likely to keep hold on their power during the budget debate.

Klobuchar told me yesterday that the stimulus negotiations could "potentially" serve as a model for the drafting of the budget. That prospect may give progressives heartburn if increased spending and tax hikes for the wealthy are put on the chopping block to assuage centrist concerns. But as Landrieu explained, the Democratic skeptics have yet to delve into details about what exactly is worth resisting in the president's budget.

Using the public record, however, let's take a look at what motivates three five of the key centrists in this debate:

Nelson: The Nebraska senator, alongside Maine GOP Sens. Olympia Snowe and Susan Collins, was a major player in the stimulus debate. He has left the door open to supporting a rollback of the Bush tax breaks for wealthy families, as I noted yesterday, but is by no means a sure thing. One budget proposal that's almost certain to run aground on opposition from Nelson is the lowering of the earnings cap on farms that are eligible to receive government subsidy aid, from $750,000 to $500,000.

Landrieu: The Louisianan voted for the 2001 Bush tax breaks and could well oppose a budget that assumes their expiration. She was also one of four Democrats to oppose last year's climate change bill, making her a potential foe of the Obama budget's assumption of more than $75 billion in revenue from auctioning off carbon emissions permits. "Let's enjoin the battle on this year's budget," she said yesterday. "I'm looking forward to a great debate."

Bayh: He voted against the Bush tax cuts in 2001, but appeared to make a 180-degree turn this week, telling Politico that "before we raise revenue, we first should look to see if there are ways we can cut back on spending." Bayh is also a prime candidate to put the brakes on a budgetary effort to address climate change. As Newsweek noted this week, most of his state's power is generated by the coal industry:

[Bayh] has voiced concerns about the Obama proposal. But Bayh won't get to ask questions in [the energy] committee, because the "cap and trade" plan was taken from his jurisdiction and instead given to Sen. Barbara Boxer of California, a strong proponent of the idea.

Never mind that Bayh isn't the chairman of the energy committee -- Sen. Jeff Bingaman (D-NM) is. But you get the picture.

Late Update: Here's a bit more background on two more of the senators who attended the first meeting of budget skeptics.

Klobuchar: This freshman senator was part of the bipartisan group that worked out a deal to increase the amount of coastal land open to offshore drilling while enhancing alternative energy benefits -- so her record shows an affinity for reaching consensus with the GOP.

But she sounds hardly reluctant to repeal the Bush tax cuts for the wealthiest earners, telling MSNBC last week that her constituents "are not whining that much" about rolling back breaks for those making more than $250,000. Klobuchar also defended Obama's vow to cut the deficit in half by the end of his first term: "I actually do" believe he can do it, she said.

Begich: As a very new arrival in the Senate, his ultimate stance on the budget may depend more on its potential benefits for his state than on its overall spending levels. In fact, his office issued a release last week touting the budget's multiple goodies for Alaska in detail.