A few points on the unfolding drama:
1. The virtually unanimous opinion of the news media is that Trump has suffered catastrophic damage due to the release of the Access Hollywood tape. This may well be correct! But media interpretations of breaking news events like this are much more likely to overstate than understate their ultimate importance. Even Mitt Romney's "47 percent" comments in 2012 did not actually change many voters' minds, despite confident media assertions to the contrary. There's nothing wrong with waiting until we see some evidence of the electorate's response to this development before we draw conclusions about the extent of the damage done.
2. This doesn't mean that there won't be any damage. Trump was already losing the election, and in fact was already sliding in the polls relative to Hillary Clinton, before this story broke. Even if no current Trump supporters defect from his candidacy as a result of the latest revelations, he is in the position of needing to win over some voters who are currently undecided or supporting another candidate. That task becomes even harder now, and every day that passes without good news for Trump is itself bad news for Trump.
3. There's a lot of chatter about the possibility of Trump being replaced as the Republican candidate, perhaps with his running mate Mike Pence. Several Republican officeholders have expressed a preference for such a maneuver, while a friend told me last night that some of her liberal acquaintances were worried about a GOP switcheroo that could allow the party to escape its Trump problem unscathed. But this is a highly improbable scenario for a variety of reasons, and proposing it allows prominent Republicans to indulge in wishful thinking while sidestepping the question of whether they will in fact continue to back Trump against Hillary Clinton if he remains the party's nominee. (Given Pence's support of Trump, it's hard to argue that the party would be able to shed the Trump association even if Trump himself were to be jettisoned somehow.)
4. Most top Republicans will conclude this weekend that Trump himself is toast and that focus must shift to protecting the Republican majorities in Congress. But this is more complicated than it looks. In "blue" and "purple" states and congressional districts where Clinton is favored to win, individual Republican candidates are likely to renounce Trump (following the lead of New Hampshire senator Kelly Ayotte and Nevada senate candidate Joe Heck, who did so today). These candidates need some support from Clinton voters to be elected themselves, and they don't want to spend the final weeks of the campaign defending Trump's behavior.
But other Republican leaders may worry that a full-scale rejection of Trump by the national party will depress turnout across the board, bringing normally Republican-leaning constituencies into play. This would be a nightmare scenario for control of the House in particular, which Democrats can only win by making inroads into habitually "red" districts. For Paul Ryan and Mitch McConnell, the solution may be to retain a degree of ambiguity on Trump himself while stressing the unacceptability of Hillary Clinton, especially a potential President Hillary Clinton who is unencumbered by a Republican Congress. It is quite possible that even reduced Republican enthusiasm for Trump himself will not translate into a significant dropoff in Republican turnout simply because party supporters can still be mobilized to vote against Clinton and the rest of the Democratic ticket.
5. It's also important to remember that the time horizons of Republican politicians extend beyond November 2016. The ascension of Hillary Clinton to the presidency, if it occurs, will spark a combustion on the American right that will probably exceed the conservative backlash against the elections of Obama in 2008 and Bill Clinton in 1992, which in both cases resulted in purges within the GOP. Republican leaders who already view their party's popular base with a mix of puzzlement and fear will very much wish to avoid attracting blame for perceived complicity in a Hillary Clinton election, which is why Ted Cruz gave in to conservative pressure and endorsed Trump in late September after months of holding out. As Republicans consider how best to handle the latest Trump news, they will seek to avoid leaving themselves vulnerable to charges from fellow partisans that they cared more about "political correctness" than the (supposed) looming national catastrophe of another Clinton in the White House.