donald j. trump entered the third presidential debate wednesday night trailing by a wider margin in national polls than any modern candidate who has ever gone on to win the presidency. whatever you think of his performance, it is hard to argue that it was the sort of resounding victory that he needed to change the trajectory of the race. the post-debate polls suggested that hillary clinton won by a comfortable, if not overwhelming, margin. the cnn insta-poll gave her a 13-point win, 52 percent to 39 percent. yougov gave her a 10-point victory. the big post-debate story lines were probably even worse for mr. trump, with most coverage focusing on his refusal to commit to an acceptance of the election result. obviously, this is not what mr. trump needed with just three weeks to go. a majority of voters have persistent concerns about his fitness for the presidency, and dislike him personally. here<u+2019>s what to watch for over the last few weeks of the race. is there a trump comeback? mr. trump has only an 8 percent chance of winning the presidency, according to the upshot<u+2019>s forecasting model . there are two basic ways he could win: one is that the polls are simply wrong. another is that mr. trump will rally in the polls over the next few weeks. realistically, he will need both to go his way. right now, it<u+2019>s fine to just focus on the big picture <u+2014> whether that<u+2019>s the national polls, with mrs. clinton holding a lead of around seven percentage points, or the various models. he needs a significant and broad tightening: he would be a clear underdog even if he trailed by half as much as he does now heading into election day. the electoral college isn<u+2019>t a significant consideration at the moment. he trails by too much. if the race tightens, it will be worth looking at whether mr. trump has made a breakthrough in mrs. clinton<u+2019>s firewall <u+2014> states like pennsylvania and new hampshire. but we<u+2019>re just not at that point yet. can clinton build a landslide? there<u+2019>s no formal definition of a <u+201c>landslide.<u+201d> but if a double-digit victory counts as one, a clinton landslide is a lot likelier than a victory for mr. trump. there are political reasons a clinton landslide might matter. a clear defeat for mr. trump, for instance, might dissuade republicans from trying to pursue a similar message in the future. more concretely, it could help democrats down the ballot. the national polls offer a pretty clear sense of whether mrs. clinton is running away with the race. but it<u+2019>s worth focusing on her share of the vote, not just her margin. if she can get into the upper 40s or over 50 percent in the polls of a four-way race, or well over 50 percent in the two-way race, it<u+2019>ll be a sign that she is locking in her big edge. if the next tier of leaning-republican states <u+2014> like missouri, indiana, texas, south carolina or alaska <u+2014> start looking like true tossups, that would be another sign of a landslide. can republicans hold the senate? republicans are still competitive in the race for the senate, and they<u+2019>ll probably need to win races in three of these six states to retain control of the chamber: pennsylvania, indiana, nevada, new hampshire, north carolina and missouri. right now, all six races could go either way. whether the democrats start to pull away in these states is one of the most important things to watch this week. can the democrats put the house in play? if hillary clinton starts to pull away, control of the house will loom as a possibility for the democrats. it<u+2019>s not likely. it<u+2019>s very hard to identify a realistic path for the democrats to get the seats they need. but if you want a quick sense of whether the democrats can dream, follow the generic congressional ballot <u+2014> which asks voters which party they would prefer to control congress. right now, the democrats lead by around four or five points on that question. they might need to double that to have a chance of retaking the chamber. the upshot provides news, analysis and graphics about politics, policy and everyday life. follow us on facebook and twitter . sign up for our newsletter.
with debates done, here<u+2019>s what to look for in final weeks
nate cohn