Mr. Gingrich said Mr. Geithner's failure to pay Social Security and Medicare taxes for 2001, 2002, 2003 and 2004 should automatically disqualify him, and that if Mr. Obama doesn't withdraw the nomination Republicans should make a stand.
"Senate Republicans should make it clear that they will not permit a tax evader to become the secretary of the Treasury," the Georgia Republican told The Washington Times. "Even after he was explicitly sent material telling him he had to pay them he did not do so."
Before taking the oath of the presidency on Tuesday, Mr. Obama had called Mr. Geithner's tax problems an "innocent mistake" that should not stand in the way of his confirmation. The Senate Finance Committee hearing on the Geithner confirmation is scheduled to begin Wednesday, the first full day of the new Obama administration.
Information that Mr. Geithner had failed to pay $34,000 in taxes some years ago had already wrecked Senate Democrats' plans to win approval of his appointment as Treasury secretary before Mr. Obama's inauguration Tuesday. But to the consternation of many Republicans outside - and a few inside - the halls of Congress, bipartisan backing of the Geithner appointment has been held up in the Senate.
Some leading Senate Republicans publicly have avoided confrontation of the nomination with the economy in dire straights.
"Now is not the time to think in small political terms," South Carolina Sen. Lindsey Graham said recently. "I don't see any desire by the Republican Party to play 'gotcha' on this."
Mr. Graham said he thinks Mr. Geithner is "the right guy" for the job.
But Mr. Gingrich insists that it "would be wrong for someone who did not pay taxes to become secretary of the Treasury in charge of getting taxes from the rest of us. It would be doubly wrong to appoint him in an administration which intends to raise taxes on the rest of us."
At least one conservative Republican strategist outside the Washington Beltway, however, urged caution in avoiding the appearance of confrontation for the sake of confrontation with the new Democratic order.
"It's a political mistake to give the Obama administration any excuses for not getting us out of this financial crisis," former Florida Republican Party Chairman Al Cardenas told The Times. "From what I understand, this tax problem was embarrassing and a blemish for a future secretary of the Treasury and under other circumstances I might opine differently.
"But it is not a matter of such moral turpitude that it warrants delaying the implementation of a recovery plan, even if I disagree with it in many respects. ... Let's let them succeed or fail with their proposed team."
But before the inauguration Tuesday, two of the Senate's most conservative members - Arizona Sen. Jon Kyl, the Finance Committee's second-ranking Republican member, and Kentucky Sen. Jim Bunning, another Republican on the committee - had balked at early confirmation hearings.
"Republicans seem to be in awe of Obama, with no real response from the current Republican leaders, from [Senate Minority Leader Mitch] McConnell and the other so-called congressional leaders," said former Reagan administration official Michael Karem, a Louisville attorney.
"Maybe they think it's OK that he didn't pay his taxes until he got caught," Mr. Karem said. "They talk about leadership. What leadership? They talk about Republican participles, but yet they keep quiet. They fear being taken on by the media and far left."
Mr. Gingrich thinks Republicans have a clear issue of principles on which to take their stand.
"Geithner has had to pay $33,000 in back taxes and $15,000 in interest," Mr. Gingrich said. "The IRS did not fine him. Ask small businesses how many of them think they could avoid paying self-employment Social Security and Medicare taxes for seven years and not be fined."