As 100 United States senators sit in solemn judgment, the matter of President Bill Clinton and former White House intern Monica Lewinsky has at last entered its final stage: a focused and direct confrontation over evidence. For months, the affair has seemed at times to be about anything but the facts. It's been obscured by spin, soured by partisanship, and drowned out by talk-show chatter. Its unpredictable ferocity has claimed one House Speaker and his presumptive heir, and stripped the shell of privacy from lawmakers and Linda Tripp alike. Now, in the quasi-judicial setting of a Senate trial, House prosecutors and Clinton defenders will likely be forced to argue about specific events, instead of continuing to talk past one another. That means each will try to sell the Senate "jury" its own view of independent counsel Kenneth Starr's voluminous, but largely circumstantial, case. If briefs filed in recent days are any guide, Mr. Clinton's lawyers will try to get senators to look at events in isolation, weighing the White House explanation for each. Prosecutors want the senators to use a panoramic lens, hoping to persuade them that an array of suspicious events is, in fact, an insidious scheme. Things that might seem innocent on their face "may well take on a sinister, or even criminal, connotation when viewed in the context of the whole plot," says a brief filed by House prosecutors. That's a point of view the White House has dismissed as the product of an overheated imagination, with spokesman Joe Lockhart comparing the House managers' brief to a cheap mystery novel. Three things to watch As House managers and Clinton lawyers present the substance of their cases in days to come, a number of key issues bear watching, say experts. One is the amount of time the prosecution spends on the impeachment charge that alleges obstruction of justice, as opposed to the time it spends on perjury. Evidence that Clinton may have committed perjury before Mr. Starr's grand jury has long been considered the strongest aspect of the House case. But several factors may lead Rep. Henry Hyde (R) of Illinois and other House managers to emphasize the obstruction evidence, instead. Laying out extensive detail about perjury would necessarily involve talking about the nature of the sexual relationship between Clinton and Ms. Lewinsky - something no one on Capitol Hill is eager to do. This is reflected in the somewhat contradictory statement in the House managers' brief that such details are "relevant, [but] need not be detailed ... in this document." Furthermore, the perjury charge may have been discounted, in the sense that a significant number of lawmakers have said lying about sex may not be an impeachable offense. Obstruction of justice might be seen as a more serious offense, and one with distinctly Watergate-like overtones. Many of the witnesses whom House managers have said they would like to call, such as White House lawyer Bruce Lindsey and Clinton secretary Betty Currie, would bear only on the obstruction charge. "The obstruction case is the sleeper here," says Jonathan Turley, a law professor at George Washington University here. House managers might well explore the nature of Clinton friend Vernon Jordan's job hunt for Lewinsky, for instance. The White House has pointed out it began long before Clinton had any idea that the former intern would come to the attention of Paula Jones's lawyers, and thus the public. But the search intensified only after Lewinsky was subpoenaed in the Jones case, says the House brief. A second point to watch might be the way the White House handles Lewinsky's words. Her testimony is both the center of the case against Clinton - particularly on the perjury charge - and his best defense. She contradicts him on the nature of their relationship, but she also declared that "no one ever asked me to lie" and that Mr. Jordan's job search for her was not intended to buy her silence. White House lawyers will thus have to strike a delicate balance of challenging one aspect of her testimony, without undermining her overall credibility. "I don't see her as a harmful witness to him in the final analysis," says Stan Brand, a Washington lawyer at Brand, Lowell & Ryan. More specifics, please A third crucial point might be the success, or lack thereof, of the Clinton team's concerted attack on the packaging of the case. Its defense brief charges that the articles of impeachment are vague - they don't say which statements are alleged to be perjurious, for instance - and lump too many allegations together. The House brief also attempts to resurrect charges based on Clinton's behavior in his deposition to lawyers in the Jones case, says the president's team. Because the House defeated an article of impeachment concerning Clinton's Jones deposition, such an attempt is unwarranted, his defenders say. Staff writers Francine Kiefer and James N. Thurman contributed to this article.