After months of dismissing outright the prospects for comprehensive tax reform, Washington insiders are beginning to take notice of a bipartisan, bicameral effort to enact comprehensive tax reform.

Conservative Republicans favoring a flatter, simpler tax structure have been particular encouraged with an approach that has put all special interest-favored tax provisions in the tax code under consideration for elimination. House Ways and Means Committee Chairman Dave Camp, R-Mich., is leading this effort in the House; in the Senate, Finance Committee Chairman Max Baucus, D-Mont., and the committee's ranking Republicans, Orrin Hatch, of Utah, are in charge.

But pessimism still reigns among many on the right, in part because most Democrats, led by President Obama, have a different idea of what tax reform means. Typically, their vision includes higher taxes on wealthier individuals and small businesses. This discouragement was evident in a letter to Baucus and Hatch that Sen. Marco Rubio, R-Fla., was due to publicize Wednesday morning.

In the letter, Rubio also questioned whether enough Republicans were interested in the "pro-growth tax reform needed to reinvigorate our economy," writing that "some want to use tax reform as a vehicle to redistribute income; others want to raise net tax revenue to fund an even more expansive government."

Meanwhile, Sen. Ted Cruz, R-Texas, has called for abolishing the scandal-scarred Internal Revenue Service.

"I will say, I am most encouraged by the recent reports that Sen. Baucus and Sen. Hatch are suggesting that we start from zero-based tax reform  that we start w/ zero deductions, a blank slate," Cruz told the Washington Examiner earlier this month. "If they stick to that, I think that is a very positive measure for major tax reform."