George Allen held no public events Wednesday, instead hunkering down to prepare for his fifth Senate debate against Timothy M. Kaine and their final one before Election Day.

Kaine (D) stuck to plans to tour a Colonial Heights hummus plant that he had helped draw to the state as governor but also squeezed in time for debate practice.

The two former governors, vying for the seat held by retiring Sen. James Webb (D), will meet for an hour-long debate starting at 7 p.m. Thursday at Virginia Tech in Blacksburg. It will air statewide on C-SPAN and will be shown on WSLS, the NBC affiliate in Roanoke that is sponsoring the debate with Virginia Tech.

“This will be the last time that people can have a statewide opportunity to see the two individuals together,” said Robert E. Denton Jr., a Virginia Tech political communications professor who with WSLS anchor Jay Warren will moderate the debate.

Kaine has been squeezing in debate prep sessions whenever he finds time between events. On Tuesday, when a gathering with Northern Virginia women wrapped up at a Dulles hotel, a Kaine aide hustled into the room carrying a portable lectern for a quick practice round.

During these mock debates, the role of Allen has been played by David Hallock, an aide to Sen. Mark R. Warner (D) who has also advised Kaine in the past. During Kaine’s 2005 run for governor, Hallock took on the part of Republican nominee Jerry Kilgore in debate practice sessions.

Allen (R) and a group of advisers met for debate preparations Wednesday with Christopher Nolen, a Richmond lawyer active in Republican politics, playing Kaine, according to a participant who spoke on the condition of anonymity because the campaign had not authorized the release of that information. Nolen, a senior campaign aide to Kilgore in the 2005 gubernatorial race, sometimes played Kaine in mock debates in that race.

Denton expects both candidates to play it extremely safe in the debate given the tightness of their race, one of a handful of contests that could shift the balance of power in the Senate.

“If one was really further behind, there might be a little more risk taking,” Denton said.

The rules negotiated by the candidates will make for fewer questions and probably fewer surprises, Denton said. The candidate asked a question will get 90 seconds to answer, his opponent will get 90 seconds to respond and then the first candidate will get a 60-second rebuttal. The format will lend itself to relatively long answers and a short list of topics.

“I must confess, the rules that were negotiated limit the total number of questions that can be asked. We will be lucky to have eight questions from us,” Denton said, noting that each candidate will have the opportunity to pose one question to his opponent.

Kaine and Allen first debated in December in Richmond, before Allen had even secured the GOP nomination. They also squared off in Hot Springs in July, McLean in September and Richmond 10 days ago.

The tone shifted markedly between their past two debates. Both men took pains to say something nice about the other in their muted matchup in McLean, with Allen lavishing praise on Kaine’s response to the massacre at Virginia Tech and Kaine giving Allen kudos for his love of campaigning.

They were harsher in Richmond, with each lobbing personal attacks.

Allen characterized Kaine as having been a part-time governor, jetting across the country as chairman of the Democratic National Committee while his state sank into the worst of the recession.

Kaine argued that Allen was too mean-spirited and partisan to fix what ails Washington, twice invoking Allen’s 1994 exhortation to fellow Republicans to knock Democrats’ “soft teeth down their whiny throats.”

Denton predicted that the men would tone the attacks down this time around, particularly in light of reports that women — seen as a crucial demographic in the Senate race — generally recoiled from the combative tone of Tuesday’s presidential debate.

Kaine and Allen will probably try to look assertive, he said, but not overly aggressive.

Ben Pershing contributed to this report.