Baker will answer senators' questions today during a hearing of the Senate Foreign Relations Committee, which includes three Democratic presidential hopefuls and Sen. Chuck Hagel (Neb.), the chamber's most forceful Republican critic of the war, who also is mulling a White House bid.

Opponents of Bush's plan to send more troops are likely to ask Baker about the study group's conclusion that "[s]ustained increases in U.S. troop levels would not solve the fundamental cause of violence in Iraq, which is the absence of national reconciliation."

To support the president's proposal, Baker may note that the study group also agreed that it could support a short-term surge of American combat forces to stabilize Baghdad or speed the training of Iraqi government forces. However, given the broader conclusion that more troops will not end the violence, Baker may have to admit that adding more troops will not be as effective as the Bush administration and its congressional allies argue.

Baker also may be asked about the study group's conclusions that the "situation in Baghdad and several provinces is dire," the "level of violence is high and growing," and "there is great suffering, and the daily lives of many Iraqis show little or no improvement."

Those assessments contradict the positive picture that Vice President Dick Cheney painted during a nationally televised interview last week.

"There's problems - ongoing problems - but we have in fact accomplished our objectives of getting rid of the old regime, and there is a new regime in place that's been here for less than a year, far too soon for you guys to write them off," Cheney told CNN's Wolf Blitzer. "Bottom line is that we've had enormous successes and we will continue to have enormous successes."

Baker has had a long history with Bush, his father and Cheney. Both Baker and Cheney worked for President Gerald Ford. Baker managed George H.W. Bush's 1980 presidential campaign, and later served as secretary of state during his administration, when Cheney held the post of secretary of defense.

More recently, Baker oversaw the vote recount effort in Florida that swung the 2000 presidential election to the Bush-Cheney ticket.

While the decision on whether to appear before Congress has been a delicate dance for Baker, it has also been a sensitive subject for congressional Democrats who do not want to scare off prominent Republicans from testifying at their hearings. A sign of the deference Democrats are willing to show, they are not expected to put Baker under oath tomorrow.

Baker originally declined to testify before the Democrat-controlled Senate Foreign Relations and House Foreign Affairs panels. Hamilton testified on his own before the House committee on Jan. 19 and was scheduled also to make a solo appearance around that time before the Senate.

Upon learning that Hamilton would go to the Senate alone, Baker changed his mind and agreed to testify as long as the hearing date was postponed until a week after Bush's State of the Union address, almost three weeks after the president unveiled his new plan for the war, according to sources knowledgeable of what led to today's scheduled appearance.

While Baker wavered on whether to appear before the Senate, he did not reveal any second thoughts about skipping a request to testify in the House, where lawmakers are younger and have a reputation for being less decorous than their Senate counterparts.

"Baker really didn't want to testify and felt like the report spoke for itself," a policy assistant to Baker, John Williams, said. "But Hamilton wanted to testify before Congress.

"In an effort to keep a bipartisan approach he [Baker] worked with Biden's office to find a time when he thought the two of them could meet," Williams added, referring to the chairman of the Senate Foreign Relations Committee, Sen. Joseph Biden (D-Del.).

Williams also said that Baker only wanted to make one appearance before Congress.

"The fact is that he wanted to do one," Williams said. "He didn't want to come back and forth and back and forth, and the Senate worked with his schedule."

If Baker had agreed to the Senate's first proposed hearing date of Jan. 18, however, he could have testified before both chambers on successive days, presumably requiring only one roundtrip flight from Houston.

Williams disputed that Baker's testimony necessarily would undercut Bush's proposed troop surge, noting that the study group said it could support a short-term surge.

"That's not inconsistent with what the president is doing right now," Williams said. He also argued that it did not make sense that Baker would seek to postpone his congressional appearance because Bush unveiled his plan for more troops eight days before the Senate Foreign Relations Committee's original hearing date.

Williams said the Jan. 18 and 19 hearing dates simply did not fit into Baker's schedule, but he could not immediately say what Baker was doing on those days.

For now, at least, Democrats are accepting scheduling conflicts as reasons to appear before their committees.

"Originally Secretary Baker was not available on Jan. 18 (when Lee Hamilton was scheduled to testify), but his scheduled opened up on Jan. 30," Senate Foreign Relations Committee spokeswoman Elizabeth Alexander said. "To accommodate both Baker and Hamilton's schedules - so they could appear together - the SFRC postponed the hearing until Jan. 30."