Fresh off the contentious battle over the latest war supplemental, White House budget chief Rob Portman and Congressional Republicans are hunkering down for a series of bruising battles with Democrats on spending and taxes.

Setting up a tough slog through this year’s spending bills, Portman reiterated veto threats last week against any bills that exceed the president’s requests or include too many earmarks, adding that he also expects a showdown at some point over Democratic tax hikes.

“Look at the supplemental,” said Portman, the former House Member who now serves as director of the Office of Management and Budget. “We do have a veto. We will use the veto if necessary.”

Portman said he will recommend a veto against any bill that exceeds the president’s request until Democrats show they will live by the president’s overall request of $933 billion.

Given that Democrats plan to spend $23 billion more than that to bolster programs such as education, veterans’ benefits and health care, the biggest fiscal confrontation since the 1995 government shutdown looms.

Portman’s hard-line position has been bolstered by House conservatives, who have circulated a letter vowing to uphold the vetoes and hope to cross the threshold of 146 signatures — the number of votes needed to sustain a veto — sometime this week.

Two key appropriators have signed on — Appropriations ranking member Jerry Lewis (R-Calif.) and moderate Rep. Ray LaHood (R-Ill.). LaHood had earlier refused to rule out voting for an override.

Lewis, meanwhile, has been fuming at Appropriations Chairman David Obey (D-Wis.) over a series of perceived slights, including being shut out of decisions on the stopgap fiscal 2007 spending bill and the Iraq War supplemental, as well as Obey’s decision to withhold earmarks from fiscal 2008 bills until conference reports are drafted, which Lewis believes violates House rules.

Lewis spokesman Jim Specht said that Lewis “always agreed with the thought that the president should veto bills that significantly increase spending” but had not immediately signed on to the letter, thinking that there was a chance Democrats could keep to the overall level even if some bills exceeded the president’s request. But now that doesn’t seem possible.

“It seemed clear that the Democrats were never going to find ways to make up the difference,” he said.

Kirstin Brost, spokeswoman for Obey, ridiculed the letter and the veto threat.

“It’s ridiculous they would make a veto threat on bills before they’ve even seen them,” she said, adding, “We tried to do the president’s budget last year and we were unable to enact nine of 11 appropriations bills.”

Four spending bills have cleared House subcommittees to date, and Democrats are expected to add money to every one of the appropriations bills with the possible exception of Defense. The four bills unveiled so far are each at least $1 billion over the president’s request, and the military construction, Veterans Administration and related agencies bill is more than $4 billion over. House appropriators will formally set allocations for the measures this week, with bills moving to the floor starting next week.

“We certainly welcome Mr. Lewis” to the letter, said Brad Dayspring, a spokesman for Rep. Jeb Hensarling (Texas), chairman of the conservative Republican Study Committee, who said the latest count was 138 signatures. “I think it speaks to the strength of the Republican Party willing to stand by the president’s number. … We’re very pleased with the work that Portman has done and we’re confident that the White House is going to stick to its guns and veto these bills.”

Left-leaning groups, meanwhile, plan to launch a campaign Tuesday intended to put pressure on moderate Republicans to vote to override spending vetoes, said Moira Mack, a spokeswoman for the Emergency Campaign for America’s Priorities.

A coalition including the American Federation of State, County and Municipal Employees is circulating a letter opposing the vetoes and grass-roots efforts that are being planned to target moderate Republicans, she said.

“Appropriations battles tend to pit advocacy groups against each other since they are competing for funding, but the threat of a veto has mobilized labor unions, service providers and advocacy groups to come together,” she said. “I think it’s going to be really difficult for Republicans who sign on to this letter to keep their promise,” she said.

But Portman argued that the Bush administration already has compromised by allowing $17 billion in additional spending in the Iraq supplemental, much of which he argued was not true emergency spending and wouldn’t even be spent until fiscal 2008 anyway.

Portman contends that the extra spending in the supplemental should make it much easier for Congress to stay within the $933 billion Bush proposed, by freeing up room for other spending. And Portman, who said the administration soon will revise this year’s deficit figure down to about $200 billion, contends that restraint in domestic accounts has contributed substantially to the shrinking deficit.

Portman added that other factors also will be considered in weighing vetoes, including policy riders on issues such as abortion, as well as the level of earmarks. Portman pledged to shine a bright spotlight on earmarks, asking agency heads to report promptly on earmarks in all of the bills.

But Portman said he was “very disappointed” that Obey will not disclose earmarks until conference reports are compiled, which Obey attributed to a lack of time to properly vet each one due to an extension — sought by Lewis — to the deadline for submitting requests, and to the work done on the supplemental and finishing last year’s bills.

“The administration did nothing on earmarks for six years,” Brost said. “Obey said he wanted to cut the amount spent on earmarks in half, and we will have full disclosure on every earmark.”

Portman added that his biggest disappointment with Democrats this year is not the spending or expectations that Democrats will seek to pass tax increases, but the lack of any movement on reining in the costs of entitlement programs.

“I just see no appetite on the Hill for getting that done,” Portman said. “I don’t see the prospect of doing something serious on Medicare, Medicaid and Social Security, at least in the short term. I hope I’m wrong. I’m just not optimistic right now that we have a willing partner.”