After facing months of criticism about whether he could successfully provide a 20 percent, across-the-board tax cut to all Americans while not adding to the debt, not giving the rich a tax cut, and not raising taxes on the middle class, Mitt Romney has finally admitted that he would need “flexibility” to make his plan work.

“There’s no question if you start off with that as the premise, the math fits the premise,” Romney told the Des Moines Register editorial board Tuesday. “Meaning, I don’t start off with the math and then say, ‘Oh, does this actually help or hurt?’ No, no. I start off with a very fundamental principle, which is we want to reduce the burden on middle-income taxpayers, and we’re not going to provide a tax break to high-income taxpayers. That’s the foundation. And then there’s flexibility as to how to do that.”

Romney has proposed various tax plans and outlined numerous principles his plan should uphold once it is in place, so ThinkProgress decided to put together a timeline of Romney’s tax proposals to see just how flexible he has been:

9/6/11: Romney’s First Tax Cut For The Rich

Promising not to cut taxes for the rich, Romney proposes a plan that would extend the Bush tax cuts, eliminate capital gains taxes for those making under $200,000, cut corporate taxes, and eliminate the estate tax. In all, it adds up to a $6.6-trillion cut that would have little benefit for the middle class, which doesn’t enjoy the same benefits from a capital gains cut as the rich.

2/22/12: Romney Introduces A New Tax Plan

Under pressure from conservatives, Romney scraps his first plan in favor of the current plan, which maintains the Bush tax cuts, provides another 20-percent rate reduction for all Americans, cuts corporate taxes, and eliminates the estate tax. Romney says he will eliminate unspecified tax loopholes and deductions to pay for the plan. Romney promises he won’t cut taxes for the rich. He also promises his plan won’t add to the deficit.

2/22/12: Romney Promises To Cut Taxes For The 1 Percent

After criticism from fellow Republican presidential candidates, Romney asserts at a primary debate that “we’re going to cut taxes on everyone across the country by 20 percent, including the top 1 percent,” contradicting his previous assertion that he wouldn’t cut taxes for the rich.

3/1/12: Tax Plan Will Lead To $4.8 Trillion In Lost Revenue

The nonpartisan Tax Policy Center scores Romney’s plan, finding that it would cost $4.8 trillion over the next 10 years. TPC does not take into account Romney’s plan to pay for his tax cuts, since he hasn’t yet proposed a specific way to do so. TPC found that Romney’s plan would give the average millionaire nearly $260,000 in tax cuts.

4/15/12: Romney Names Two Deductions He’d Eliminate

Romney tells donors that he would “probably eliminate” the mortgage interest deduction on second homes for high-income Americans, as well as deductions for state and local income taxes. That still falls far short of paying for his plan.

4/16/12: Advisers Walk Those Comments Back

Romney aides walk back those comments, saying Romney’s fundraiser remarks were only in response to questions from donors and shouldn’t be taken as policy proposals.

6/4/12: A $5 Million Tax Cut For Himself

Citizens for Tax Justice issues a study finding Romney would save $5 million under his own tax plan.

7/17/12: Media Begins To Press Romney To Name Deductions, He Refuses

Romney refuses to name deductions he would eliminate when pressed by CBS host Bob Schieffer. He also claims his tax plan won’t reduce the “share of the tax burden” paid by the wealthiest Americans, a canard meant to hide his massive tax cut for the wealthy.

8/1/12: Romney’s Plan Would Raise Taxes On The Middle Class

The Tax Policy Center returns to the Romney tax plan, attempting to find out how he would pay for it. TPC finds that there is not enough revenue to be gained through the elimination of deductions for high-income earners to pay for the tax cut, so to avoid adding to the deficit, Romney would have to raise taxes on the middle class by as much as $2,000.

8/9/12: Conservatives Start Coming To His Defense

Matt Jensen of the American Enterprise Institute responds to the TPC study by noting that it didn’t take into account Romney’s proposal to eliminate the deduction for interest on state and local bonds (an investment break that, according to general Republican thinking, should receive a tax break). Romney said previously that such a deduction was “on the table,” but has not said it would definitely be eliminated under his plan.

8/16/12: Even With Conservative Additions, The Plan Doesn’t Add Up

TPC re-analyzes the plan and concludes that Jensen assumed more savings than could be realized from the elimination of the deduction for interest on state and local bonds. “Our main result still holds,” TPC writes.

8/23/12: Romney’s Corporate Tax Cuts Also Raise Middle Class Taxes

The Tax Policy Center analyzes Romney’s corporate tax plan, which would reduce revenues by $900 billion over 10 years. TPC had previously assumed Romney would pay for his corporate tax cut by eliminating corporate deductions, but that isn’t the case, according to the Romney campaign. TPC finds that Romney’s corporate cut would cost middle class taxpayers another $2,000 if he wants to maintain current levels of revenue.

8/28/12: Romney Advisers Adopt Bad Math

Romney adviser Martin Feldstein writes an editorial in the Wall Street Journal dismissing the TPC analysis. Feldstein’s math, however, excludes the corporate tax cut, redefines middle class, and overstates savings that could be gained from the elimination of upper-income tax breaks.

9/12: GOP Advisers Adopt Bad Math, Part II

Princeton professor Harvey Rosen, a former Bush adviser, publishes a study that assumes Romney’s plan will work because it will generate enough economic growth to pay any revenue loss, ignoring that the same logic was applied to other GOP-led tax cuts, including those signed by George W. Bush.

9/12: Romney Cites Five Debunked “Studies” To Back Up His Plan

Romney begins citing “five studies” that show his tax plan can work. Those studies are most likely Jensen’s, Feldstein’s, and Rosen’s, all of which have had their problems exposed. The other two are thought to be Wall Street Journal editorials that assert Romney’s plan is “mathematically possible” but add no new information.

9/9/12: Conservative Tax Expert Admits The Plan Doesn’t Work

Alan Viard, a tax expert at the conservative American Enterprise Institute, tells the New York Times that Romney will have “to cut rates significantly less than 20 percent if he wants to honor his other goals.”

9/10/12: Romney Adviser Still Can’t Name A Deduction He’d Eliminate

Romney adviser Tara Wall can’t name a single loophole or deduction Romney would close to help pay for his plan. Instead, she says “energy independence.”

9/25/12: Romney Adviser Admits The Plan Doesn’t Work

Romney adviser Kevin Hassett, also a fellow at AEI, says that if Romney can’t pay for his plan by eliminating deductions, he “would have a different change in rates.” That is, the tax cut would be smaller.

9/30/12: Paul Ryan Can’t Explain The Math Behind The Plan

Asked to explain the math of Romney’s tax plan on Fox News Sunday, vice presidential nominee Paul Ryan says, “I don’t have time.”

10/3/12: Romney Proposes A New Idea — It Still Doesn’t Work

Ahead of the first presidential debate, Romney floats a new idea to pay for his plan: he will cap the amount of deductions each taxpayer can use at $17,000. This proposal would still fall well short of paying for Romney’s plan, according to TPC. And worse, it could curtail deductions for housing and health care that benefit the middle class.

10/3/12: Romney Walks Back His Own Support

In the first presidential debate, Romney seems to walk back support for his own tax plan. When President Obama criticizes the plan for adding to the deficit or raising taxes on the middle class, Romney says he would “absolutely not” support such a plan. Seemingly ignoring TPC, an AEI expert, and his own adviser, he then reasserts that his plan will cut tax rates by 20 percent and adhere to three principles: it will not add to the deficit, it will not cut taxes on the rich, and it will not raise taxes on the middle class.

10/3/12: Romney’s Web Site Debunks His Own Claims About The Wealthy

Romney’s campaign web site refutes his debate claim that he won’t cut taxes on the rich.

10/9/12: Romney Tweaks His Newest Idea, Making His Tax Math Even ‘Fuzzier’

On CNN, Romney adopts the idea to cap tax deductions he proposed just a week earlier. Instead of capping deductions at $17,000, he’ll now cap them at either $25,000 or $50,000. As the Washington Post’s Suzy Khimm notes, though, this makes the math of Romney’s tax plan even harder to work out. Placing the cap at $25,000, the Tax Policy Center found, would make it possible to avoid raising taxes on the middle class. It would also generate significantly less revenue. Placing it at $50,000, though, would render it irrelevant, since even taxpayers in the top 1 percent averaged only $43,208 in deductions last year.

10/9/12: Romney Needs “Flexibility”

Romney admits to the Des Moines Register that he will need “flexibility” to make his tax plan add up. At this point, it is no longer clear what tax plan Romney actually supports.